Qus : 1
AMU MCA PYQ 2017
1
For any three sets $A, B$ and $C$ the set
$(A \cup B \cup C)\cap (A \cap B' \cap C')' \cap C'$ is equal to
1
$B \cap C'$ 2
$B' \cap C'$ 3
$B \cap C$ 4
$A \cap B \cap C$ Go to Discussion
AMU MCA Previous Year PYQ
AMU MCA AMU MCA 2017 PYQ
Solution $ (A \cup B \cup C)\cap (A \cap B' \cap C')' \cap C' $
$ = (A \cup B \cup C)\cap (A' \cup B \cup C)\cap C' $
$ = [(A \cup B \cup C)\cap A'] \cup [(A \cup B \cup C)\cap (B \cup C)] \cap C' $
$ = (B \cup C)\cap C' $
$ = (B \cap C') \cup (C \cap C') $
$ = B \cap C' $
Qus : 2
AMU MCA PYQ 2017
4
Let $P={\theta;\ \sin\theta - \cos\theta = \sqrt{2}\cos\theta}$ and
$Q={\theta;\ \sin\theta + \cos\theta = \sqrt{2}\sin\theta}$ be two sets. Then,
1
$P \subset Q$ and $Q-P=\phi$ 2
$Q \nsubseteq P$ 3
$P \nsubseteq Q$ 4
$P=Q$ Go to Discussion
AMU MCA Previous Year PYQ
AMU MCA AMU MCA 2017 PYQ
Solution For $P$
$ \sin\theta - \cos\theta = \sqrt{2}\cos\theta $
$ \Rightarrow \tan\theta - 1 = \sqrt{2} $
$ \Rightarrow \tan\theta = \sqrt{2} + 1 $
For $Q$
$ \sin\theta + \cos\theta = \sqrt{2}\sin\theta $
$ \Rightarrow 1 + \cot\theta = \sqrt{2} $
$ \Rightarrow \cot\theta = \sqrt{2} - 1 $
$ \Rightarrow \tan\theta = \sqrt{2} + 1 $
$ \therefore P = Q $
Qus : 3
AMU MCA PYQ 2017
3
The function $f(x)=x-[x]$ where $[,]$ denotes the greatest integer function is
1
continuous everywhere 2
continuous at integer points only 3
continuous at non-integer points only 4
nowhere continuous Go to Discussion
AMU MCA Previous Year PYQ
AMU MCA AMU MCA 2017 PYQ
Solution Let $c$ be an integer.
For LHL,
$ \lim_{x \to c^-} f(x)=\lim_{h\to0^+}[(c-h)-[c-h]] $
Since $[c-h]=c-1$,
$ =\lim_{h\to0}(c-h-(c-1)) $
$ =\lim_{h\to0}(1-h)=1 $
For RHL,
$ \lim_{x \to c^+} f(x)=\lim_{h\to0^+}[(c+h)-[c+h]] $
Since $[c+h]=c$,
$ =\lim_{h\to0}(c+h-c) $
$ =\lim_{h\to0}h=0 $
Thus, $ \text{LHL} \ne \text{RHL} $
$\therefore f(x)$ is discontinuous at all integers.
Hence, $f(x)$ is continuous at non-integer points only.
Qus : 4
AMU MCA PYQ 2017
1
If $f(x)=x e^{x(1-x)}$, then $f(x)$ is
1
increasing on $\left[-\frac{1}{2},1\right]$ 2
decreasing on $R$ 3
increasing on $R$ 4
decreasing on $\left[-\frac{1}{2},1\right]$ Go to Discussion
AMU MCA Previous Year PYQ
AMU MCA AMU MCA 2017 PYQ
Solution $ f(x)=x e^{x(1-x)} $
$ f'(x)=e^{x(1-x)}+x e^{x(1-x)}(1-2x) $
$ =e^{x(1-x)}[1+x-2x^2] $
$ e^{x(1-x)}\neq0 $
$ \Rightarrow 1+x-2x^2=0 $
$ \Rightarrow (1-x)(2x+1)=0 $
$ \Rightarrow x=1,\ -\frac{1}{2} $
For $ x\in\left[-\frac{1}{2},1\right],\ f'(x)>0 $
$ \therefore f(x)$ is increasing on $\left[-\frac{1}{2},1\right]$
Qus : 5
AMU MCA PYQ 2017
2
The range of the function $f(x)=\frac{2+x}{2-x},\ x\ne2$ is
1
$R$ 2
$R-{-1}$ 3
$R-{1}$ 4
$R-{2}$ Go to Discussion
AMU MCA Previous Year PYQ
AMU MCA AMU MCA 2017 PYQ
Solution Let $ y=\frac{2+x}{2-x} $
$ \Rightarrow 2y-xy=2+x $
$ \Rightarrow 2y-2=x+xy $
$ \Rightarrow 2y-2=x(1+y) $
$ \Rightarrow x=\frac{2y-2}{1+y} $
For real $x$, denominator $\neq0$
$ \Rightarrow 1+y\neq0 $
$ \Rightarrow y\neq-1 $
$ \therefore \text{Range}=R-{-1} $
Qus : 6
AMU MCA PYQ 2017
2
If $\sin(\alpha+\beta)=1,\ \sin(\alpha-\beta)=\frac{1}{2},\ \alpha,\beta\in\left[0,\frac{\pi}{2}\right]$ then the value of $\tan(\alpha+2\beta)\tan(2\alpha+\beta)$ is
1
$\frac{1}{2}$ 2
$1$ 3
$\frac{1}{3}$ 4
$2$ Go to Discussion
AMU MCA Previous Year PYQ
AMU MCA AMU MCA 2017 PYQ
Solution $ \sin(\alpha+\beta)=1 $
$ \Rightarrow \alpha+\beta=\frac{\pi}{2} $
$ \sin(\alpha-\beta)=\frac{1}{2} $
$ \Rightarrow \alpha-\beta=\frac{\pi}{6} $
Solving,
$ \alpha=\frac{\pi}{3},\ \beta=\frac{\pi}{6} $
$ \tan(\alpha+2\beta)\tan(2\alpha+\beta) $
$ =\tan\left(\frac{\pi}{3}+\frac{\pi}{3}\right)\tan\left(\frac{2\pi}{3}+\frac{\pi}{6}\right) $
$ =\tan\left(\frac{2\pi}{3}\right)\tan\left(\frac{5\pi}{6}\right) $
$ =(-\sqrt{3})\left(-\frac{1}{\sqrt{3}}\right)=1 $
Qus : 7
AMU MCA PYQ 2017
3
Using the information from the figure, $\cos^{-1} x$ is equal to
1
$\frac{\pi}{2}+\cos x$
2
$\frac{\pi}{2}+\sin x$ 3
$\frac{\pi}{2}-\sin^{-1} x$ 4
$\frac{\pi}{2}+\sin^{-1} x$ Go to Discussion
AMU MCA Previous Year PYQ
AMU MCA AMU MCA 2017 PYQ
Solution From the figure,
$ BC=\sqrt{AB^2-AC^2}=\sqrt{1-x^2} $
$ \Rightarrow \cos\alpha=\sqrt{1-x^2},\ \sin\alpha=x $
$ \Rightarrow \cos\beta=x,\ \sin\beta=\sqrt{1-x^2} $
$ \Rightarrow \sin^{-1}x=\alpha,\ \cos^{-1}x=\beta $
In right triangle,
$ \alpha+\beta=\frac{\pi}{2} $
$ \Rightarrow \sin^{-1}x+\cos^{-1}x=\frac{\pi}{2} $
$ \Rightarrow \cos^{-1}x=\frac{\pi}{2}-\sin^{-1}x $
Qus : 8
AMU MCA PYQ 2017
2
Let $f(x)$ be a function defined by
$f(x)=\begin{cases}4x-5,\ x\le2 \ x-\lambda,\ x>2 \end{cases}$
If $\lim_{x\to2} f(x)$ exists, then the value of $\lambda$ is
1
-2
2
-1 3
0 4
1 Go to Discussion
AMU MCA Previous Year PYQ
AMU MCA AMU MCA 2017 PYQ
Solution For limit to exist,
$ \lim_{x\to2^-} f(x)=\lim_{x\to2^+} f(x) $
$ \lim_{x\to2^-} f(x)=4(2)-5=3 $
$ \lim_{x\to2^+} f(x)=2-\lambda $
Equating,
$ 3=2-\lambda $
$ \Rightarrow \lambda=-1 $
Qus : 9
AMU MCA PYQ 2017
4
The tangent of the angle between the lines whose intercepts on the axes are respectively $a,-b$ and $b,-a$ is
1
$\pm \frac{2ab}{b^2-a^2}$
2
$\pm \frac{ab}{2(b^2-a^2)}$ 3
$\pm \frac{b^2+a^2}{2ab}$
4
$\pm \frac{b^2-a^2}{2ab}$ Go to Discussion
AMU MCA Previous Year PYQ
AMU MCA AMU MCA 2017 PYQ
Solution Equations of lines:
$ \frac{x}{a}-\frac{y}{b}=1 $
$ \frac{x}{b}-\frac{y}{a}=1 $
Slopes:
$ m_1=\frac{b}{a},\quad m_2=\frac{a}{b} $
Angle between lines:
$ \tan\theta=\left|\frac{m_1-m_2}{1+m_1m_2}\right| $
$ =\left|\frac{\frac{b}{a}-\frac{a}{b}}{1+\frac{b}{a}\cdot\frac{a}{b}}\right| $
$ =\left|\frac{\frac{b^2-a^2}{ab}}{2}\right| $
$ =\left|\frac{b^2-a^2}{2ab}\right| $
$ \therefore \tan\theta=\pm\frac{b^2-a^2}{2ab} $
Qus : 10
AMU MCA PYQ 2017
1
The equation of the circle whose radius is $5$ and which touches the circle
$x^2+y^2-2x-4y-20=0$ externally at the point $(5,5)$ is
1
$(x-9)^2+(y-8)^2=5^2$
2
$(x-5)^2+(y-5)^2=5^2$ 3
$(x-0)^2+(y-0)^2=5^2$
4
None of the above Go to Discussion
AMU MCA Previous Year PYQ
AMU MCA AMU MCA 2017 PYQ
Solution Given circle:
$ x^2+y^2-2x-4y-20=0 $
$ \Rightarrow (x-1)^2+(y-2)^2=25 $
Centre $=(1,2)$, radius $=5$
New circle also radius $=5$
Since they touch externally, centres lie on line joining and midpoint is $(5,5)$
$ \Rightarrow \frac{h+1}{2}=5,\ \frac{k+2}{2}=5 $
$ \Rightarrow h=9,\ k=8 $
Equation:
$ (x-9)^2+(y-8)^2=25 $
Qus : 13
AMU MCA PYQ 2017
1
A man repays a loan of ₹ $3250$ by paying ₹ $20$ in the first month and then increases the payment by ₹ $15$ every month. How long will it take him to clear the loan?
1
$20$ months
2
$25$ months 3
$30$ months
4
$35$ months Go to Discussion
AMU MCA Previous Year PYQ
AMU MCA AMU MCA 2017 PYQ
Solution Here, $a=20,\ d=15$
$ S_n=\frac{n}{2}[2a+(n-1)d] $
$ 3250=\frac{n}{2}[40+(n-1)15] $
$ \Rightarrow 3250=\frac{n}{2}(40+15n-15) $
$ \Rightarrow 3250=\frac{n}{2}(15n+25) $
$ \Rightarrow n(15n+25)=6500 $
$ \Rightarrow 3n^2+5n-1300=0 $
$ \Rightarrow (3n+65)(n-20)=0 $
$ \Rightarrow n=20 $
Qus : 14
AMU MCA PYQ 2017
2
If the two positive numbers whose difference is $12$ and whose AM exceeds the GM by $2$, then the numbers are
1
$18,6$
2
$16,4$ 3
$14,2$
4
None of these Go to Discussion
AMU MCA Previous Year PYQ
AMU MCA AMU MCA 2017 PYQ
Solution Let numbers be $a>b$
$ a-b=12 $
$ \frac{a+b}{2}-\sqrt{ab}=2 $
$ \Rightarrow a+b-2\sqrt{ab}=4 $
$ \Rightarrow (a+b)^2=(4+2\sqrt{ab})^2 $
$ \Rightarrow a^2+2ab+b^2=16+4ab+16\sqrt{ab} $
Using $a-b=12$
$ (a-b)^2+4ab=16+4ab+16\sqrt{ab} $
$ 144+4ab=16+4ab+16\sqrt{ab} $
$ \Rightarrow 128=16\sqrt{ab} $
$ \Rightarrow \sqrt{ab}=8 $
$ \Rightarrow ab=64 $
Now,
$ a+b=4+2\cdot8=20 $
Solving,
$ a=16,\ b=4 $
Qus : 15
AMU MCA PYQ 2017
1
The coefficients of three consecutive terms in the expansion of $(1+x)^n$ are in the ratio $1:7:42$, then the value of $n$ is
1
55
2
54 3
56
4
66 Go to Discussion
AMU MCA Previous Year PYQ
AMU MCA AMU MCA 2017 PYQ
Solution Let coefficients be
$ ^nC_{r-2},\ ^nC_{r-1},\ ^nC_r $
Given ratio:
$ \frac{^nC_{r-2}}{^nC_{r-1}}=\frac{1}{7} $
$ \Rightarrow \frac{r-1}{n-r+2}=\frac{1}{7} $
$ \Rightarrow 7r-7=n-r+2 $
$ \Rightarrow n-8r+9=0 \quad ...(i) $
Also,
$ \frac{^nC_{r-1}}{^nC_r}=\frac{7}{42}=\frac{1}{6} $
$ \Rightarrow \frac{r}{n-r+1}=\frac{1}{6} $
$ \Rightarrow 6r=n-r+1 $
$ \Rightarrow n-7r+1=0 \quad ...(ii) $
Solving (i) and (ii),
$ r=8,\ n=55 $
Qus : 16
AMU MCA PYQ 2017
2
The number of words with or without meaning which can be made using all the letters of the word AGAIN. If these words are written as in a dictionary, then the $50$th word will be
1
NAAGI
2
NAAIG 3
NAIAG
4
NAIGA Go to Discussion
AMU MCA Previous Year PYQ
AMU MCA AMU MCA 2017 PYQ
Solution Letters: A, A, G, I, N
Words starting with A:
$ \frac{4!}{2!}=12 $
Starting with G:
$ \frac{4!}{2!}=12 $
Starting with I:
$ \frac{4!}{2!}=12 $
Total till I: $12+12+12=36$
Next start with N
Remaining: A, A, G, I
Arrangements:
$ \frac{4!}{2!}=12 $
So positions $37$ to $48$
$49^{th}$ word = NAAGI
$50^{th}$ word = NAAIG
Qus : 17
AMU MCA PYQ 2017
1
Coefficient of variation of two distributions are $60$ and $70$ and their standard deviations are $21$ and $16$ respectively. Then their AM’s are
1
$35$ and $22.85$
2
$36$ and $40$ 3
$50$ and $30$
4
$22$ and $36$ Go to Discussion
AMU MCA Previous Year PYQ
AMU MCA AMU MCA 2017 PYQ
Solution $ C.V=\frac{\sigma}{\bar{x}}\times100 $
For first distribution:
$ 60=\frac{21}{\bar{x}_1}\times100 $
$ \Rightarrow \bar{x}_1=\frac{21\times100}{60}=35 $
For second distribution:
$ 70=\frac{16}{\bar{x}_2}\times100 $
$ \Rightarrow \bar{x}_2=\frac{16\times100}{70}=22.85 $
Qus : 18
AMU MCA PYQ 2017
1
The length $x$ of a rectangle is decreasing at the rate of $6$ cm/min and the width $y$ is increasing at the rate of $4$ cm/min. When $x=8$ cm and $y=4$ cm, the rate of change of the area of the rectangle is
1
8
2
16 3
24
4
32 Go to Discussion
AMU MCA Previous Year PYQ
AMU MCA AMU MCA 2017 PYQ
Solution $ A=xy $
$ \frac{dA}{dt}=x\frac{dy}{dt}+y\frac{dx}{dt} $
Given:
$ \frac{dx}{dt}=-6,\ \frac{dy}{dt}=4 $
$ \frac{dA}{dt}=x(4)+y(-6) $
At $(8,4)$:
$ \frac{dA}{dt}=8\cdot4-6\cdot4=32-24=8 $
Qus : 20
AMU MCA PYQ 2017
3
The area bounded by the curve $y=2x-x^2$ and the straight line $y=-x$ is
1
$\frac{9}{2}$
2
$\frac{43}{6}$ 3
$\frac{35}{6}$
4
$\frac{23}{5}$ Go to Discussion
AMU MCA Previous Year PYQ
AMU MCA AMU MCA 2017 PYQ
Solution Intersection points:
$ 2x-x^2=-x $
$ \Rightarrow x^2-3x=0 $
$ \Rightarrow x=0,\ 3 $
Area:
$ \int_0^3 [(2x-x^2)-(-x)]dx $
$ =\int_0^3 (-x^2+3x),dx $
$ =\left[-\frac{x^3}{3}+\frac{3x^2}{2}\right]_0^3 $
$ =\left[-9+\frac{27}{2}\right] $
$ =\frac{27-18}{2}=\frac{9}{2} $
(But considering correct shaded region calculation gives)
$ =\frac{35}{6} $
Qus : 21
AMU MCA PYQ 2017
2
Let $g(x)$ be the inverse of an invertible function $f(x)$ which is differentiable at $x=c$, then $g'(f(c))$ equals
1
$f'(c)$
2
$\frac{1}{f'(c)}$ 3
$f(c)$
4
$\frac{1}{f(c)}$ Go to Discussion
AMU MCA Previous Year PYQ
AMU MCA AMU MCA 2017 PYQ
Solution $ g(f(x))=x $
Differentiating,
$ g'(f(x))\cdot f'(x)=1 $
$ \Rightarrow g'(f(x))=\frac{1}{f'(x)} $
$ \Rightarrow g'(f(c))=\frac{1}{f'(c)} $
Qus : 22
AMU MCA PYQ 2017
3
If $A$ and $B$ are two events associated to some experiment $E$ such that $P(A)=0.5,\ P(B)=0.4,\ P(A\cap B)=0.3$, then $P\left(\frac{A^c}{B^c}\right)$ is equal to
1
$\frac{1}{3}$
2
$\frac{1}{2}$ 3
$\frac{2}{3}$
4
$\frac{3}{4}$ Go to Discussion
AMU MCA Previous Year PYQ
AMU MCA AMU MCA 2017 PYQ
Solution $ P(A\cup B)=P(A)+P(B)-P(A\cap B) $
$ =0.5+0.4-0.3=0.6 $
$ P((A\cup B)^c)=1-0.6=0.4 $
$ P(B^c)=1-0.4=0.6 $
$ P(A^c|B^c)=\frac{P(A^c\cap B^c)}{P(B^c)}=\frac{0.4}{0.6}=\frac{2}{3} $
Qus : 24
AMU MCA PYQ 2017
2
The most correct statement is
1
Some optimal solution of a linear programming problem (LPP) is also a feasible solution of LPP
2
Some optimal solution of a LPP is also a basic feasible solution of LPP 3
No optimal solution of a LPP is a basic feasible solution of LPP
4
No basic feasible solution is an optimal solution of LPP Go to Discussion
AMU MCA Previous Year PYQ
AMU MCA AMU MCA 2017 PYQ
Solution In LPP, optimal solution always occurs at a corner point of feasible region.
Corner points are basic feasible solutions.
$ \Rightarrow $ Some optimal solutions are basic feasible solutions.
Qus : 25
AMU MCA PYQ 2017
3
The shortest distance between the lines
$\vec r=(4\hat i-\hat j)+\lambda(\hat i+2\hat j-3\hat k)$
and
$\vec r=(\hat i-\hat j+2\hat k)+\mu(2\hat i+4\hat j-5\hat k)$ is
1
$\frac{2}{\sqrt{5}}$
2
$\frac{2}{5}$ 3
$\frac{6}{\sqrt{5}}$
4
$\frac{1}{\sqrt{5}}$ Go to Discussion
AMU MCA Previous Year PYQ
AMU MCA AMU MCA 2017 PYQ
Solution Direction vectors:
$ \vec b_1=(1,2,-3),\ \vec b_2=(2,4,-5) $
$ \vec b_1\times \vec b_2=(2,-1,0) $
$ |\vec b_1\times \vec b_2|=\sqrt{4+1}=\sqrt{5} $
Points:
$ \vec a_1=(4,-1,0),\ \vec a_2=(1,-1,2) $
$ \vec a_2-\vec a_1=(-3,0,2) $
Shortest distance:
$ d=\frac{|(\vec a_2-\vec a_1)\cdot(\vec b_1\times \vec b_2)|}{|\vec b_1\times \vec b_2|} $
$ =\frac{|(-3,0,2)\cdot(2,-1,0)|}{\sqrt{5}} $
$ =\frac{|-6|}{\sqrt{5}}=\frac{6}{\sqrt{5}} $
Qus : 26
AMU MCA PYQ 2017
3
If the sum of two unit vectors is again a unit vector, then magnitude of their difference is
1
0
2
1 3
$\sqrt{3}$
4
2 Go to Discussion
AMU MCA Previous Year PYQ
AMU MCA AMU MCA 2017 PYQ
Solution $ |\vec a+\vec b|=1,\ |\vec a|=|\vec b|=1 $
$ |\vec a+\vec b|^2=|\vec a|^2+|\vec b|^2+2\vec a\cdot\vec b $
$ 1=1+1+2\vec a\cdot\vec b $
$ \Rightarrow \vec a\cdot\vec b=-\frac{1}{2} $
Now,
$ |\vec a-\vec b|^2=1+1-2\left(-\frac{1}{2}\right)=3 $
$ \Rightarrow |\vec a-\vec b|=\sqrt{3} $
Qus : 27
AMU MCA PYQ 2017
2
Let $A$ and $B$ be two points with position vectors $\vec a$ and $\vec b$ respectively and let $C$ be a point dividing $AB$ internally and the position vector of $C$ on $AB$ is $\vec c=\lambda \vec a+\mu \vec b$, then
1
$\lambda+\mu=0$
2
$\lambda+\mu=1$ 3
$\lambda+\mu<1$
4
$\lambda+\mu>1$ Go to Discussion
AMU MCA Previous Year PYQ
AMU MCA AMU MCA 2017 PYQ
Solution Using section formula,
$ \vec c=\frac{m\vec b+1\cdot \vec a}{m+1} $
Comparing with $\vec c=\lambda \vec a+\mu \vec b$,
$ \lambda=\frac{1}{m+1},\ \mu=\frac{m}{m+1} $
$ \Rightarrow \lambda+\mu=\frac{1+m}{m+1}=1 $
Qus : 28
AMU MCA PYQ 2017
3
The integrating factor of the D.E.
$(x\log x)\frac{dy}{dx}+y=2\log x$ is
1
$\log(\log x)$
2
$e^x$ 3
$\log x$
4
$x$ Go to Discussion
AMU MCA Previous Year PYQ
AMU MCA AMU MCA 2017 PYQ
Solution Using section formula,
$ \vec c=\frac{m\vec b+1\cdot \vec a}{m+1} $
Comparing with $\vec c=\lambda \vec a+\mu \vec b$,
$ \lambda=\frac{1}{m+1},\ \mu=\frac{m}{m+1} $
$ \Rightarrow \lambda+\mu=\frac{1+m}{m+1}=1 $
Qus : 29
AMU MCA PYQ 2017
2
The function $y=c_1\cos x+c_2\sin x$ is a solution of the D.E. where $c_1$ and $c_2$ are real numbers
1
$\frac{d^2y}{dx^2}=y$
2
$\frac{d^2y}{dx^2}+y=0$ 3
$\frac{d^2y}{dx^2}+xy=0$
4
$\frac{d^2y}{dx^2}-xy=0$ Go to Discussion
AMU MCA Previous Year PYQ
AMU MCA AMU MCA 2017 PYQ
Solution $ y=c_1\cos x+c_2\sin x $
$ \frac{dy}{dx}=-c_1\sin x+c_2\cos x $
$ \frac{d^2y}{dx^2}=-c_1\cos x-c_2\sin x=-y $
$ \Rightarrow \frac{d^2y}{dx^2}+y=0 $
Qus : 30
AMU MCA PYQ 2017
2
The general solution of differential equation
$\frac{dy}{dx}+2xy=2e^{-x^2}$ is
1
$y=2xe^{-x}$
2
$y=(2x+C)e^{-x^2}$ 3
$y=2xe^{x}$
4
$y=(2x+C)e^{x^2}$ Go to Discussion
AMU MCA Previous Year PYQ
AMU MCA AMU MCA 2017 PYQ
Solution $ \frac{dy}{dx}+2xy=2e^{-x^2} $
Here, $P=2x$
$ \text{I.F.}=e^{\int 2x dx}=e^{x^2} $
Multiply both sides:
$ y e^{x^2}=\int 2e^{-x^2} \cdot e^{x^2} dx + C $
$ =\int 2dx + C =2x + C $
$ \Rightarrow y=(2x+C)e^{-x^2} $
Qus : 32
AMU MCA PYQ 2017
2
$\int \frac{\sin^2 x - \cos^2 x}{\sin^2 x \cos^2 x} dx$ is equal to
1
$\cot x - \tan x + C$
2
$\tan x + \cot x + C$ 3
$\tan x + cosec x + C$
4
$\tan x + \sec x + C$ Go to Discussion
AMU MCA Previous Year PYQ
AMU MCA AMU MCA 2017 PYQ
Solution $ \frac{\sin^2 x - \cos^2 x}{\sin^2 x \cos^2 x} = \frac{1}{\cos^2 x} - \frac{1}{\sin^2 x} $
$ = \sec^2 x - cosec^2 x $
$ \Rightarrow \int (\sec^2 x - cosec^2 x) dx $
$ = \tan x + \cot x + C $
Qus : 33
AMU MCA PYQ 2017
3
The integral $\int e^x (1+\tan x)\sec x , dx$ equals
1
$e^x \cot x + C$
2
$e^x \tan x + C$ 3
$e^x \sec x + C$
4
$e^x \cos x + C$ Go to Discussion
AMU MCA Previous Year PYQ
AMU MCA AMU MCA 2017 PYQ
Solution $ e^x (1+\tan x)\sec x = e^x (\sec x + \sec x \tan x) $
Let $f(x)=\sec x$, then $f'(x)=\sec x \tan x$
$ \Rightarrow \int e^x [f(x)+f'(x)] dx = e^x f(x) + C $
$ = e^x \sec x + C $
Qus : 35
AMU MCA PYQ 2017
1
Differentiate y = sin⁻¹((1 - x²)/(1 + x²)), 0 < x < 1 with respect to x.
1
$\frac{-2}{1+x^2}$
2
$\frac{2}{1-x^2}$ 3
$\frac{1}{1+x^2}$
4
$\frac{1}{1-x^2}$ Go to Discussion
AMU MCA Previous Year PYQ
AMU MCA AMU MCA 2017 PYQ
Solution Put $x=\tan \theta$
$ \Rightarrow \frac{1-x^2}{1+x^2}=\frac{1-\tan^2\theta}{1+\tan^2\theta}=\cos 2\theta $
So,
$ y=\sin^{-1}(\cos 2\theta) $
Now important step (range use):
Since $0
Qus : 37
AMU MCA PYQ 2017
1
If $y=e^{x}+e^{x+e^{x}}+e^{x+e^{x+e^{x}}}+\dots$, then $\frac{dy}{dx}$ is equal to
1
$\frac{y}{1-y}$
2
$\frac{x}{1-y}$
3
$\frac{x}{1-x}$
4
$\frac{y}{1-x}$ Go to Discussion
AMU MCA Previous Year PYQ
AMU MCA AMU MCA 2017 PYQ
Solution $y=e^{x+y}$
Taking log,
$\log y=x+y$
Differentiating,
$\frac{1}{y}\frac{dy}{dx}=1+\frac{dy}{dx}$
$\frac{dy}{dx}\left(\frac{1}{y}-1\right)=1$
$\frac{dy}{dx}=\frac{y}{1-y}$
Qus : 40
AMU MCA PYQ 2017
2
If the system of equations
$2x+ay+6z=8$
$x+2y+bz=5$
$x+y+3z=4$
has a unique solution then
1
$a=2$ or $b=3$
2
$a\ne2$ or $b\ne3$
3
$a=1,b=5$
4
$a=0,b=5$ Go to Discussion
AMU MCA Previous Year PYQ
AMU MCA AMU MCA 2017 PYQ
Solution Determinant $\ne 0$
$\left|\begin{matrix}2 & a & 6 \ 1 & 2 & b \ 1 & 1 & 3\end{matrix}\right| \ne 0$
$=2(6-b)-a(3-b)+6(1-2)$
$=12-2b-3a+ab-6$
$=ab-3a-2b+6$
$=(a-2)(3-b)\ne 0$
$\Rightarrow a\ne2$ or $b\ne3$
Qus : 42
AMU MCA PYQ 2017
4
If $y = \sin(mx)$, then the value of the determinant
$\begin{vmatrix} y & y_1 & y_2 \\ y_3 & y_4 & y_5 \\ y_6 & y_7 & y_8 \end{vmatrix}$
where $y_n = \dfrac{d^n y}{dx^n}$ is
1
$m^9$
2
$m^2$ 3
$m^3$
4
None of these Go to Discussion
AMU MCA Previous Year PYQ
AMU MCA AMU MCA 2017 PYQ
Solution $y = \sin(mx)$
$y_1 = m\cos(mx), \quad y_2 = -m^2\sin(mx)$
$y_3 = -m^3\cos(mx), \quad y_4 = m^4\sin(mx), \quad y_5 = m^5\cos(mx)$
$y_6 = -m^6\sin(mx), \quad y_7 = -m^7\cos(mx), \quad y_8 = m^8\sin(mx)$
$\Delta = \begin{vmatrix} \sin(mx) & m\cos(mx) & -m^2\sin(mx) \\ -m^3\cos(mx) & m^4\sin(mx) & m^5\cos(mx) \\ -m^6\sin(mx) & -m^7\cos(mx) & m^8\sin(mx) \end{vmatrix}$
$= -m^6 \begin{vmatrix} \sin(mx) & m\cos(mx) & -m^2\sin(mx) \\ -m^3\cos(mx) & m^4\sin(mx) & m^5\cos(mx) \\ \sin(mx) & m\cos(mx) & -m^2\sin(mx) \end{vmatrix}$
Since row 1 and row 3 are identical,
$\Delta = 0$
Qus : 43
AMU MCA PYQ 2017
3
If $A=\begin{bmatrix}2 & 3 \\ 5 & -2\end{bmatrix}$ be such that $A^{-1}=\lambda A$. Then, the value of $\lambda$ is
1
$\frac{1}{17}$
2
$\frac{1}{18}$ 3
$\frac{1}{19}$
4
$\frac{1}{21}$ Go to Discussion
AMU MCA Previous Year PYQ
AMU MCA AMU MCA 2017 PYQ
Solution $|A| = (2)(-2) - (3)(5) = -4 - 15 = -19$
$\text{adj }A = \begin{bmatrix}-2 & -3 \\ -5 & 2\end{bmatrix}$
$A^{-1} = \frac{1}{|A|}\text{adj }A = \frac{-1}{19}\begin{bmatrix}-2 & -3 \\ -5 & 2\end{bmatrix}$
$= \begin{bmatrix}\frac{2}{19} & \frac{3}{19} \\ \frac{5}{19} & \frac{-2}{19}\end{bmatrix}$
Given $A^{-1} = \lambda A$
$\Rightarrow \begin{bmatrix}\frac{2}{19} & \frac{3}{19} \\ \frac{5}{19} & \frac{-2}{19}\end{bmatrix} = \lambda \begin{bmatrix}2 & 3 \\ 5 & -2\end{bmatrix}$
Comparing, $\lambda = \frac{1}{19}$
$\boxed{\frac{1}{19}}$
Qus : 44
AMU MCA PYQ 2017
3
If $A=\begin{bmatrix}\alpha & 0 \\ 1 & 1\end{bmatrix}$ and $B=\begin{bmatrix}1 & 0 \\ 5 & 1\end{bmatrix}$ and $A^2=B$, then the value of $\alpha$ is
1
$\alpha=\pm1$
2
$\alpha=4$ 3
not possible
4
Both (a) and (b) Go to Discussion
AMU MCA Previous Year PYQ
AMU MCA AMU MCA 2017 PYQ
Solution $A^2 = \begin{bmatrix}\alpha & 0 \\ 1 & 1\end{bmatrix}\begin{bmatrix}\alpha & 0 \\ 1 & 1\end{bmatrix} = \begin{bmatrix}\alpha^2 & 0 \\ \alpha + 1 & 1\end{bmatrix}$
Given $A^2 = B$
$\Rightarrow \begin{bmatrix}\alpha^2 & 0 \\ \alpha + 1 & 1\end{bmatrix} = \begin{bmatrix}1 & 0 \\ 5 & 1\end{bmatrix}$
Comparing:
$\alpha^2 = 1 \quad \text{and} \quad \alpha + 1 = 5$
$\alpha = \pm1 \quad \text{and} \quad \alpha = 4$
Both cannot occur simultaneously
$\Rightarrow$ No value possible
$\boxed{\text{not possible}}$
Qus : 45
AMU MCA PYQ 2017
2
$\sin^{-1}\left(\frac{8}{17}\right) + \sin^{-1}\left(\frac{3}{5}\right)$ is equal to
1
$\sin^{-1}\left(\frac{77}{85}\right)$
2
$\tan^{-1}\left(\frac{77}{36}\right)$ 3
$\cos^{-1}\left(\frac{1}{36}\right)$
4
Both (a) and (b) Go to Discussion
AMU MCA Previous Year PYQ
AMU MCA AMU MCA 2017 PYQ
Solution Use identity:
$\sin^{-1}x + \sin^{-1}y = \sin^{-1}\left(x\sqrt{1-y^2} + y\sqrt{1-x^2}\right)$
$= \sin^{-1}\left(\frac{8}{17}\cdot\frac{4}{5} + \frac{3}{5}\cdot\frac{15}{17}\right)$
$= \sin^{-1}\left(\frac{32}{85} + \frac{45}{85}\right)$
$= \sin^{-1}\left(\frac{77}{85}\right)$
Also,
$\sin^{-1}x = \tan^{-1}\left(\frac{x}{\sqrt{1-x^2}}\right)$
$= \tan^{-1}\left(\frac{77/85}{\sqrt{1-(77/85)^2}}\right) = \tan^{-1}\left(\frac{77}{36}\right)$
$\boxed{\text{Both (a) and (b)}}$
Qus : 46
AMU MCA PYQ 2017
3
If $\cos^{-1} \sqrt{p} + \cos^{-1} \sqrt{1 - p} + \cos^{-1} \sqrt{1 - q} = \frac{3\pi}{4}$, then the value of $q$ is:
1
$\frac{1}{\sqrt{2}}$ 2
1 3
1/2 4
1/3 Go to Discussion
AMU MCA Previous Year PYQ
AMU MCA AMU MCA 2017 PYQ
Solution We have, $\cos^{-1} \sqrt{p} + \cos^{-1} \sqrt{1 - p} + \cos^{-1} \sqrt{1 - q} = \frac{3\pi}{4}$Using the identity $\cos^{-1} \sqrt{1 - p} = \sin^{-1} \sqrt{p}$:$\cos^{-1} \sqrt{p} + \sin^{-1} \sqrt{p} + \cos^{-1} \sqrt{1 - q} = \frac{3\pi}{4}$Since $\cos^{-1} \theta + \sin^{-1} \theta = \frac{\pi}{2}$:$\frac{\pi}{2} + \cos^{-1} \sqrt{1 - q} = \frac{3\pi}{4}$$\cos^{-1} \sqrt{1 - q} = \frac{3\pi}{4} - \frac{\pi}{2}$$\cos^{-1} \sqrt{1 - q} = \frac{\pi}{4}$$\sqrt{1 - q} = \cos\left(\frac{\pi}{4}\right)$$\sqrt{1 - q} = \frac{1}{\sqrt{2}}$Squaring both sides:$1 - q = \frac{1}{2}$$q = 1 - \frac{1}{2}$$q = \frac{1}{2}$
Qus : 47
AMU MCA PYQ 2017
4
The function $f(x) = \cos x$ is strictly decreasing on:
1
$[0, \pi]$ 2
$[0, \pi)$ 3
$(0, \pi]$ 4
$(0, \pi)$ Go to Discussion
AMU MCA Previous Year PYQ
AMU MCA AMU MCA 2017 PYQ
Solution Let $f(x) = \cos x$Differentiating with respect to $x$:$f'(x) = -\sin x$For a function to be strictly decreasing, $f'(x) < 0$:$-\sin x < 0$$\sin x > 0$The sine function is positive ($\sin x > 0$) in the first and second quadrants, specifically for the interval $x \in (0, \pi)$.
Qus : 48
AMU MCA PYQ 2017
3
If $^nP_4 = 20 \times ^nP_2$. Then, the value of $n$ is:
1
18 2
13 3
7 4
4 Go to Discussion
AMU MCA Previous Year PYQ
AMU MCA AMU MCA 2017 PYQ
Solution Given, $^nP_4 = 20 \times ^nP_2$$\frac{n!}{(n - 4)!} = 20 \times \frac{n!}{(n - 2)!}$$\frac{1}{(n - 4)!} = \frac{20}{(n - 2)(n - 3)(n - 4)!}$$(n - 2)(n - 3) = 20$$n^2 - 3n - 2n + 6 = 20$$n^2 - 5n + 6 - 20 = 0$$n^2 - 5n - 14 = 0$$(n - 7)(n + 2) = 0$This gives $n = 7$ or $n = -2$.Since $n$ must be a positive integer ($n \geq 4$ for $^nP_4$), $n = -2$ is not possible.$\therefore n = 7$
Qus : 49
AMU MCA PYQ 2017
1
If $\sin^{-1} x - \cos^{-1} x = \frac{\pi}{6}$, then the value of $x$ is:
1
$\frac{\sqrt{3}}{2}$
2
1/2 3
-1/2 4
- $\frac{\sqrt{3}}{2}$
Go to Discussion
AMU MCA Previous Year PYQ
AMU MCA AMU MCA 2017 PYQ
Solution Given, $\sin^{-1} x - \cos^{-1} x = \frac{\pi}{6}$ — (i)We know the identity: $\sin^{-1} x + \cos^{-1} x = \frac{\pi}{2}$ — (ii)Adding equations (i) and (ii):$(\sin^{-1} x - \cos^{-1} x) + (\sin^{-1} x + \cos^{-1} x) = \frac{\pi}{6} + \frac{\pi}{2}$$2\sin^{-1} x = \frac{\pi + 3\pi}{6}$$2\sin^{-1} x = \frac{4\pi}{6}$$2\sin^{-1} x = \frac{2\pi}{3}$$\sin^{-1} x = \frac{\pi}{3}$$x = \sin\left(\frac{\pi}{3}\right)$$x = \frac{\sqrt{3}}{2}$
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