JEE MAIN - Mathematics (2020 - 7th January Evening Slot)
1
Let $${a_1}$$
, $${a_2}$$
, $${a_3}$$
,....... be a G.P. such that $${a_1}$$
< 0, $${a_1}$$
+ $${a_2}$$
= 4 and $${a_3}$$
+ $${a_4}$$
= 16. If $$\sum\limits_{i = 1}^9 {{a_i}} = 4\lambda $$, then $$\lambda $$ is
equal to:
Answer
(B)
-171
2
The coefficient of x7
in the expression
(1 + x)10 + x(1 + x)9
+ x2(1 + x)8
+ ......+ x10 is:
Answer
(B)
330
3
The number of ordered pairs (r, k) for which 6.35Cr
= (k2 - 3). 36Cr + 1, where k is an integer, is :
Answer
(D)
4
4
The value of $$\alpha $$ for which
$$4\alpha \int\limits_{ - 1}^2 {{e^{ - \alpha \left| x \right|}}dx} = 5$$, is:
Answer
(A)
$${\log _e}2$$
5
The locus of the mid-points of the perpendiculars drawn from points on the line, x = 2y to the line
x = y is :
Answer
(D)
5x - 7y = 0
6
If the function ƒ defined on $$\left( { - {1 \over 3},{1 \over 3}} \right)$$ by
If the mean and variance of eight numbers 3, 7, 9, 12, 13, 20, x and y be 10 and 25 respectively,
then x.y is equal to _______.
Answer
54
8
If the system of linear equations,
x + y + z = 6
x + 2y + 3z = 10
3x + 2y + $$\lambda $$z = $$\mu $$
has more than two solutions, then $$\mu $$ - $$\lambda $$2
is equal to ______.
Answer
13
9
If the foot of the perpendicular drawn from the point (1, 0, 3) on a line passing through ($$\alpha $$, 7, 1)
is
$$\left( {{5 \over 3},{7 \over 3},{{17} \over 3}} \right)$$, then $$\alpha $$ is equal to______.
Answer
4
10
Let ƒ(x) be a polynomial of degree 5 such that x = ±1 are its critical points.
If $$\mathop {\lim }\limits_{x \to 0} \left( {2 + {{f\left( x \right)} \over {{x^3}}}} \right) = 4$$, then which one of the following is not true?
Answer
(B)
x = 1 is a point of minima and x = -1 is a point of maxima of ƒ.
11
Let X = {n $$ \in $$ N : 1 $$ \le $$ n $$ \le $$ 50}. If
A = {n $$ \in $$ X: n is a multiple of 2} and
B = {n $$ \in $$ X: n is a multiple of 7}, then the number of elements in the smallest subset of X
containing both A and B is ________.
Answer
29
12
If $${{3 + i\sin \theta } \over {4 - i\cos \theta }}$$, $$\theta $$ $$ \in $$ [0, 2$$\theta $$], is a real number, then an argument of sin$$\theta $$ + icos$$\theta $$ is :
If $$\theta $$1
and $$\theta $$2
be respectively the smallest and the largest values of $$\theta $$ in (0, 2$$\pi $$) - {$$\pi $$} which satisfy
the equation,
2cot2$$\theta $$ - $${5 \over {\sin \theta }}$$ + 4 = 0, then
$$\int\limits_{{\theta _1}}^{{\theta _2}} {{{\cos }^2}3\theta d\theta } $$ is equal to :
Answer
(C)
$${{\pi } \over 3}$$
14
Let y = y(x) be a function of x satisfying
$$y\sqrt {1 - {x^2}} = k - x\sqrt {1 - {y^2}} $$ where k is a constant and
$$y\left( {{1 \over 2}} \right) = - {1 \over 4}$$. Then $${{dy} \over {dx}}$$ at x = $${1 \over 2}$$, is equal to :
Answer
(B)
$$ - {{\sqrt 5 } \over 2}$$
15
Let $$\overrightarrow a $$
, $$\overrightarrow b $$
and $$\overrightarrow c $$
be three unit vectors such that
$$\overrightarrow a + \vec b + \overrightarrow c = \overrightarrow 0 $$. If $$\lambda = \overrightarrow a .\vec b + \vec b.\overrightarrow c + \overrightarrow c .\overrightarrow a $$ and
$$\overrightarrow d = \overrightarrow a \times \vec b + \vec b \times \overrightarrow c + \overrightarrow c \times \overrightarrow a $$, then the ordered pair, $$\left( {\lambda ,\overrightarrow d } \right)$$ is equal to :
Answer
(C)
$$\left( { - {3 \over 2},3\overrightarrow a \times \overrightarrow b } \right)$$
16
The area (in sq. units) of the region
{(x, y) $$ \in $$ R2 | 4x2 $$ \le $$ y $$ \le $$ 8x + 12} is :
Answer
(B)
$${{128} \over 3}$$
17
Let y = y(x) be the solution curve of the differential equation,
$$\left( {{y^2} - x} \right){{dy} \over {dx}} = 1$$, satisfying y(0) =
1. This curve intersects the x-axis at a point whose abscissa is :
Answer
(D)
2 - e
18
Let $$\alpha $$ and $$\beta $$ be the roots of the equation x2
- x - 1 = 0. If pk
= $${\left( \alpha \right)^k} + {\left( \beta \right)^k}$$
, k $$ \ge $$ 1, then which one
of the following statements is not true?