JEE MAIN - Mathematics (2019 - 10th January Evening Slot)
1
If $$\int\limits_0^x \, $$f(t) dt = x2 + $$\int\limits_x^1 \, $$ t2f(t) dt then f '$$\left( {{1 \over 2}} \right)$$ is -
Answer
(C)
$${{24} \over {25}}$$
2
Let f be a differentiable function such that f '(x) = 7 - $${3 \over 4}{{f\left( x \right)} \over x},$$ (x > 0) and f(1) $$ \ne $$ 4. Then $$\mathop {\lim }\limits_{x \to 0'} \,$$ xf$$\left( {{1 \over x}} \right)$$ :
Answer
(C)
exists and equals 4
3
Let f : ($$-$$1, 1) $$ \to $$ R be a function defined by f(x) = max $$\left\{ { - \left| x \right|, - \sqrt {1 - {x^2}} } \right\}.$$ If K be the set of all points at which f is not differentiable, then K has exactly -
Answer
(B)
three elements
4
The number of values of $$\theta $$ $$ \in $$ (0, $$\pi $$) for which the system of linear equations
x + 3y + 7z = 0
$$-$$ x + 4y + 7z = 0
(sin3$$\theta $$)x + (cos2$$\theta $$)y + 2z = 0.
has a non-trival solution, is -
Answer
(A)
two
5
The curve amongst the family of curves represented by the differential equation, (x2 – y2)dx + 2xy dy = 0 which passes through (1, 1) is :
Answer
(C)
a circle with centre on the x-axis
6
Let $$z = {\left( {{{\sqrt 3 } \over 2} + {i \over 2}} \right)^5} + {\left( {{{\sqrt 3 } \over 2} - {i \over 2}} \right)^5}.$$ If R(z) and 1(z) respectively denote the real and imaginary parts of z, then :
Answer
(C)
I(z) = 0
7
The positive value of $$\lambda $$ for which the co-efficient of x2
in the expression x2 $${\left( {\sqrt x + {\lambda \over {{x^2}}}} \right)^{10}}$$ is 720, is -
Answer
(A)
4
8
The value of $$\lambda $$ such that sum of the squares of the roots of the quadratic equation, x2 + (3 – $$\lambda $$)x + 2 = $$\lambda $$ has the least value is -
Answer
(B)
2
9
Let A = $$\left[ {\matrix{
2 & b & 1 \cr
b & {{b^2} + 1} & b \cr
1 & b & 2 \cr
} } \right]$$ where b > 0.
Then the minimum value of $${{\det \left( A \right)} \over b}$$ is -
Answer
(D)
$$2\sqrt 3 $$
10
If $$\overrightarrow \alpha $$ = $$\left( {\lambda - 2} \right)\overrightarrow a + \overrightarrow b $$ and $$\overrightarrow \beta = \left( {4\lambda - 2} \right)\overrightarrow a + 3\overrightarrow b $$ be two given vectors $$\overrightarrow a $$ and $$\overrightarrow b $$ are non-collinear. The value of $$\lambda $$ for which vectors $$\overrightarrow \alpha $$ and $$\overrightarrow \beta $$ are collinear, is -
Answer
(D)
$$-$$4
11
Let S = $$\left\{ {\left( {x,y} \right) \in {R^2}:{{{y^2}} \over {1 + r}} - {{{x^2}} \over {1 - r}}} \right\};r \ne \pm 1.$$ Then S represents :
Answer
(D)
an ellipse whose eccentricity is $$\sqrt {{2 \over {r + 1}}}$$, where r > 1
12
The value of $$\int\limits_{ - \pi /2}^{\pi /2} {{{dx} \over {\left[ x \right] + \left[ {\sin x} \right] + 4}}} ,$$ where [t] denotes the greatest integer less than or equal to t, is
Answer
(D)
$${3 \over {20}}\left( {4\pi - 3} \right)$$
13
Two vertices of a triangle are (0, 2) and (4, 3). If its orthocenter is at the origin, then its third vertex lies in which quadrant :
Answer
(C)
second
14
If $$\sum\limits_{r = 0}^{25} {\left\{ {{}^{50}{C_r}.{}^{50 - r}{C_{25 - r}}} \right\} = K\left( {^{50}{C_{25}}} \right)} ,\,\,$$ then K is equal to :
Answer
(C)
225
15
Let a1, a2, a3, ..... a10 be in G.P. with ai > 0 for i = 1, 2, ….., 10 and S be the set of pairs (r, k), r, k $$ \in $$ N (the set of natural numbers) for which
The value of $$\cos {\pi \over {{2^2}}}.\cos {\pi \over {{2^3}}}\,.....\cos {\pi \over {{2^{10}}}}.\sin {\pi \over {{2^{10}}}}$$ is -
Answer
(D)
$${1 \over {512}}$$
17
The value of $$\cot \left( {\sum\limits_{n = 1}^{19} {{{\cot }^{ - 1}}} \left( {1 + \sum\limits_{p = 1}^n {2p} } \right)} \right)$$ is :
Answer
(C)
$${{21} \over {19}}$$
18
If mean and standard deviation of 5 observations x1, x2, x3, x4, x5 are 10 and 3, respectively, then the variance of 6 observations x1, x2, ….., x5 and –50 is equal to
Answer
(B)
507.5
19
Two sides of a parallelogram are along the lines, x + y = 3 & x – y + 3 = 0. If its diagonals intersect at (2, 4), then one of its vertex is :
Answer
(D)
(3, 6)
20
A helicopter is flying along the curve given by y – x3/2 = 7, (x $$ \ge $$ 0). A soldier positioned at the point $$\left( {{1 \over 2},7} \right)$$ wants to shoot down the helicopter when it is nearest to him. Then this nearest distance is -
Answer
(A)
$${1 \over 6}\sqrt {{7 \over 3}} $$
21
If the area of an equilateral triangle inscribed in the circle x2 + y2
+ 10x + 12y + c = 0 is $$27\sqrt 3 $$ sq units then c is equal to :
Answer
(B)
25
22
If $$\int \, $$x5.e$$-$$4x3 dx = $${1 \over {48}}$$e$$-$$4x3 f(x) + C, where C is a constant of inegration, then f(x) is equal to -
Answer
(D)
$$-$$4x3 $$-$$ 1
23
The length of the chord of the parabola x2 $$=$$ 4y having equation x – $$\sqrt 2 y + 4\sqrt 2 = 0$$ is -
Answer
(B)
$$6\sqrt 3 $$
24
Let N be the set of natural numbers and two functions f and g be defined as f, g : N $$ \to $$ N such that