JEE MAIN - Mathematics (2019 - 12th April Morning Slot)

1
If ey + xy = e, the ordered pair $$\left( {{{dy} \over {dx}},{{{d^2}y} \over {d{x^2}}}} \right)$$ at x = 0 is equal to :
Answer
(B)
$$\left( { - {1 \over e},{1 \over {{e^2}}}} \right)$$
2
If $$\alpha $$ and $$\beta $$ are the roots of the equation 375x2 – 25x – 2 = 0, then $$\mathop {\lim }\limits_{n \to \infty } \sum\limits_{r = 1}^n {{\alpha ^r}} + \mathop {\lim }\limits_{n \to \infty } \sum\limits_{r = 1}^n {{\beta ^r}} $$ is equal to :
Answer
(B)
$${{29} \over {348}}$$
3
The equation |z – i| = |z – 1|, i = $$\sqrt { - 1} $$, represents :
Answer
(D)
the line through the origin with slope 1
4
If $$\int\limits_0^{{\pi \over 2}} {{{\cot x} \over {\cot x + \cos ecx}}} dx$$ = m($$\pi $$ + n), then m.n is equal to
Answer
(A)
- 1
5
For x $$ \in $$ (0, 3/2), let f(x) = $$\sqrt x $$ , g(x) = tan x and h(x) = $${{1 - {x^2}} \over {1 + {x^2}}}$$. If $$\phi $$ (x) = ((hof)og)(x), then $$\phi \left( {{\pi \over 3}} \right)$$ is equal to :
Answer
(B)
$$\tan {{11\pi } \over {12}}$$
6
The integral $$\int {{{2{x^3} - 1} \over {{x^4} + x}}} dx$$ is equal to :
(Here C is a constant of integration)
Answer
(C)
$${\log _e}\left| {{{{x^3} + 1} \over x}} \right| + C$$
7
If $$B = \left[ {\matrix{ 5 & {2\alpha } & 1 \cr 0 & 2 & 1 \cr \alpha & 3 & { - 1} \cr } } \right]$$ is the inverse of a 3 × 3 matrix A, then the sum of all values of $$\alpha $$ for which det(A) + 1 = 0, is :
Answer
(D)
1
8
If three of the six vertices of a regular hexagon are chosen at random, then the probability that the triangle formed with these chosen vertices is equilateral is :
Answer
(A)
$${1 \over {10}}$$
9
The value of $${\sin ^{ - 1}}\left( {{{12} \over {13}}} \right) - {\sin ^{ - 1}}\left( {{3 \over 5}} \right)$$ is equal to :
Answer
(B)
$${\pi \over 2} - {\sin ^{ - 1}}\left( {{{56} \over {65}}} \right)$$
10
Let f : R $$ \to $$ R be a continuously differentiable function such that f(2) = 6 and f'(2) = $${1 \over {48}}$$. If $$\int\limits_6^{f\left( x \right)} {4{t^3}} dt$$ = (x - 2)g(x), then $$\mathop {\lim }\limits_{x \to 2} g\left( x \right)$$ is equal to :
Answer
(A)
18
11
Let Sn denote the sum of the first n terms of an A.P. If S4 = 16 and S6= – 48, then S10 is equal to :
Answer
(A)
- 320
12
The equation y = sinx sin (x + 2) – sin2 (x + 1) represents a straight line lying in :
Answer
(D)
third and fourth quadrants only
13
A 2 m ladder leans against a vertical wall. If the top of the ladder begins to slide down the wall at the rate 25 cm/sec, then the rate (in cm/sec.) at which the bottom of the ladder slides away from the wall on the horizontal ground when the top of the ladder is 1 m above the ground is :
Answer
(D)
$${{25} \over {\sqrt 3 }}$$
14
Let $$\overrightarrow a = 3\widehat i + 2\widehat j + 2\widehat k$$ and $$\overrightarrow b = \widehat i + 2\widehat j - 2\widehat k$$ be two vectors. If a vector perpendicular to both the vectors $$\overrightarrow a + \overrightarrow b $$ and $$\overrightarrow a - \overrightarrow b $$ has the magnitude 12 then one such vector is :
Answer
(A)
$$4\left( {2\widehat i - 2\widehat j - \widehat k} \right)$$
15
If A is a symmetric matrix and B is a skew-symmetric matrix such that A + B = $$\left[ {\matrix{ 2 & 3 \cr 5 & { - 1} \cr } } \right]$$, then AB is equal to :
Answer
(D)
$$\left[ {\matrix{ 4 & { - 2} \cr { - 1} & { - 4} \cr } } \right]$$
16
If the data x1, x2,......., x10 is such that the mean of first four of these is 11, the mean of the remaining six is 16 and the sum of squares of all of these is 2,000 ; then the standard deviation of this data is :
Answer
(B)
2
17
If the area (in sq. units) of the region {(x, y) : y2 $$ \le $$ 4x, x + y $$ \le $$ 1, x $$ \ge $$ 0, y $$ \ge $$ 0} is a $$\sqrt 2 $$ + b, then a – b is equal to :
Answer
(C)
6
18
Consider the differential equation, $${y^2}dx + \left( {x - {1 \over y}} \right)dy = 0$$, If value of y is 1 when x = 1, then the value of x for which y = 2, is :
Answer
(A)
$${3 \over 2} - {1 \over {\sqrt e }}$$
19
If the angle of intersection at a point where the two circles with radii 5 cm and 12 cm intersect is 90o, then the length (in cm) of their common chord is :
Answer
(C)
$${{120} \over {13}}$$
20
The coefficient of x18 in the product
(1 + x) (1 – x)10 (1 + x + x2)9 is :
Answer
(D)
84
21
If m is the minimum value of k for which the function f(x) = x$$\sqrt {kx - {x^2}} $$ is increasing in the interval [0,3] and M is the maximum value of f in [0, 3] when k = m, then the ordered pair (m, M) is equal to :
Answer
(B)
$$\left( {4,3\sqrt 3 } \right)$$
22
The number of ways of choosing 10 objects out of 31 objects of which 10 are identical and the remaining 21 are distinct, is :
Answer
(B)
220