JEE MAIN - Mathematics (2020 - 2nd September Evening Slot)
1
Let a, b, c $$ \in $$ R be all non-zero and satisfy
a3 + b3 + c3 = 2. If the matrix
A = $$\left( {\matrix{
a & b & c \cr
b & c & a \cr
c & a & b \cr
} } \right)$$
satisfies ATA = I, then a value of abc can be :
Answer
(B)
$${1 \over 3}$$
2
If the equation cos4 $$\theta $$ + sin4 $$\theta $$ +
$$\lambda $$ = 0 has real
solutions for
$$\theta $$, then
$$\lambda $$ lies in the interval :
Answer
(D)
$$\left[ { - 1, - {1 \over 2}} \right]$$
3
Let f : R $$ \to $$ R be a function which satisfies
f(x + y) = f(x) + f(y) $$\forall $$ x, y $$ \in $$ R. If f(1) = 2 and
g(n) = $$\sum\limits_{k = 1}^{\left( {n - 1} \right)} {f\left( k \right)} $$, n $$ \in $$ N then the value of n, for
which g(n) = 20, is :
Answer
(C)
5
4
Let f(x) be a quadratic polynomial such that
f(–1) + f(2) = 0. If one of the roots of f(x) = 0
is 3, then its other root lies in :
Answer
(C)
(–1, 0)
5
Let n > 2 be an integer. Suppose that there are
n Metro stations in a city located along a
circular path. Each pair of stations is connected
by a straight track only. Further, each pair of
nearest stations is connected by blue line,
whereas all remaining pairs of stations are
connected by red line. If the number of red lines
is 99 times the number of blue lines, then the
value of n is :
Answer
(A)
201
6
The area (in sq. units) of an equilateral triangle
inscribed in the parabola y2 = 8x, with one of
its vertices on the vertex of this parabola, is :
Answer
(D)
$$192\sqrt 3 $$
7
Let f : (–1,
$$\infty $$)
$$ \to $$ R be defined by f(0) = 1 and
f(x) = $${1 \over x}{\log _e}\left( {1 + x} \right)$$, x $$ \ne $$ 0. Then the function f :
Let the position vectors of points 'A' and 'B' be
$$\widehat i + \widehat j + \widehat k$$ and $$2\widehat i + \widehat j + 3\widehat k$$, respectively. A point
'P' divides the line segment AB internally in the
ratio
$$\lambda $$ : 1 (
$$\lambda $$ > 0). If O is the origin and
$$\overrightarrow {OB} .\overrightarrow {OP} - 3{\left| {\overrightarrow {OA} \times \overrightarrow {OP} } \right|^2} = 6$$, then
$$\lambda $$ is equal
to______.
Answer
0.8
10
Let [t] denote the greatest integer less than or
equal to t. Then the value of $$\int\limits_1^2 {\left| {2x - \left[ {3x} \right]} \right|dx} $$ is ______.
If the variance of the terms in an increasing A.P., b1
, b2
, b3
,....,b11 is 90, then the common
difference of this A.P. is_______.
Answer
3
13
If the variance of the terms in an increasing A.P., b1
, b2
, b3
,....,b11 is 90, then the common
difference of this A.P. is_______.
Answer
3
14
The set of all possible values of
$$\theta $$ in the interval
(0, $$\pi $$) for which the points (1, 2) and (sin
$$\theta $$, cos $$\theta $$) lie on the same side of the line x + y =
1 is :
Answer
(D)
$$\left( {0,{\pi \over 2}} \right)$$
15
If a curve y = f(x), passing through the point
(1, 2), is the solution of the differential equation,
2x2dy= (2xy + y2)dx, then $$f\left( {{1 \over 2}} \right)$$ is equal to :
Answer
(B)
$${1 \over {1 + {{\log }_e}2}}$$
16
Consider a region R = {(x, y) $$ \in $$ R : x2 $$ \le $$ y $$ \le $$ 2x}.
if a line y = $$\alpha $$ divides the area of region R into
two equal parts, then which of the following is
true?
Answer
(C)
3$$\alpha $$2 - 8$$\alpha $$3/2 + 8 = 0
17
For some $$\theta \in \left( {0,{\pi \over 2}} \right)$$, if the eccentricity of the
hyperbola, x2–y2sec2$$\theta $$ = 10 is
$$\sqrt 5 $$ times the
eccentricity of the ellipse, x2sec2$$\theta $$ + y2 = 5, then
the length of the latus rectum of the ellipse, is :
The imaginary part of
$${\left( {3 + 2\sqrt { - 54} } \right)^{{1 \over 2}}} - {\left( {3 - 2\sqrt { - 54} } \right)^{{1 \over 2}}}$$ can be :
Answer
(A)
-2$$\sqrt 6 $$
20
If the sum of first 11 terms of an A.P.,
a1, a2, a3, ....
is 0 (a $$ \ne $$ 0), then the sum of the A.P.,
a1
, a3
, a5
,....., a23 is ka1
, where k is equal to :