1
WB JEE 2018
MCQ (Single Correct Answer)
+2
-0.5
Change Language
Let z1 and z2 be complex numbers such that z1 $$ \ne $$ z2 and |z1| = |z2|. If Re(z1) > 0 and Im(z2) < 0, then $${{{z_1} + {z_2}} \over {{z_1} - {z_2}}}$$ is
A
one
B
real and positive
C
real and negative
D
purely imaginary
2
WB JEE 2018
MCQ (Single Correct Answer)
+2
-0.5
Change Language
From a collection of 20 consecutive natural numbers, four are selected such that they are not consecutive. The number of such selections is
A
284 $$ \times $$ 17
B
285 $$ \times $$ 17
C
284 $$ \times $$ 16
D
285 $$ \times $$ 16
3
WB JEE 2018
MCQ (Single Correct Answer)
+2
-0.5
Change Language
The least positive integer n such that $${\left( {\matrix{ {\cos \pi /4} & {\sin \pi /4} \cr { - \sin {\pi \over 4}} & {\cos {\pi \over 4}} \cr } } \right)^n}$$ is an identity matrix of order 2 is
A
4
B
8
C
12
D
16
4
WB JEE 2018
MCQ (Single Correct Answer)
+2
-0.5
Change Language
Let $$\rho $$ be a relation defined on N, the set of natural numbers, as

$$\rho $$ = {(x, y) $$ \in $$ N $$ \times $$ N : 2x + y = 41}. Then
A
$$\rho $$ is an equivalence relzation.
B
$$\rho $$ is only reflexive relation
C
$$\rho $$ is only symmetric relation
D
$$\rho $$ is not transitive
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