1
WB JEE 2018
MCQ (Single Correct Answer)
+1
-0.25
Change Language
If $${Z_r} = \sin {{2\pi r} \over {11}} - i\cos {{2\pi r} \over {11}}$$, then $$\sum\limits_{r = 0}^{10} {{Z_r}} $$ is equal to
A
$$-$$ 1
B
0
C
i
D
$$-$$ i
2
WB JEE 2018
MCQ (Single Correct Answer)
+1
-0.25
Change Language
If z1 and z2 be two non-zero complex numbers such that $${{{z_1}} \over {{z_2}}} + {{{z_2}} \over {{z_1}}} = 1$$, then the origin and the points represented by z1 and z2
A
lie on a straight line
B
form a right angled triangle
C
form an equilateral triangle
D
form an isosceles triangle
3
WB JEE 2018
MCQ (Single Correct Answer)
+1
-0.25
Change Language
If $${b_1}{b_2} = 2({c_1} + {c_2})$$ and b1, b2, c1, c2 are all real numbers, then at least one of the equations $${x^2} + {b_1}x + {c_1} = 0$$ and $${x^2} + {b_2}x + {c_2} = 0$$ has
A
real roots
B
purely imaginary roots
C
roots of the form a + ib (a, b$$ \in $$R, ab $$ \ne $$ 0)
D
rational roots
4
WB JEE 2018
MCQ (Single Correct Answer)
+1
-0.25
Change Language
The number of selection of n objects from 2n objects of which n are identical and the rest are different, is
A
2n
B
2n $$-$$ 1
C
2n $$-$$ 1
D
2n $$-$$ 1 + 1
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