1
WB JEE 2016
MCQ (Single Correct Answer)
+1
-0.25
If $${1 \over {{}^5{C_r}}} + {1 \over {{}^6{C_r}}} = {1 \over {{}^4{C_r}}}$$, then the value of r is
A
4
B
2
C
5
D
3
2
WB JEE 2016
MCQ (Single Correct Answer)
+1
-0.25
For positive integer n, n3 + 2n is always divisible by
A
3
B
7
C
5
D
6
3
WB JEE 2016
MCQ (Single Correct Answer)
+1
-0.25
In the expansion of (x $$-$$ 1) (x $$-$$ 2) .... (x $$-$$ 18), the coefficient of x17 is
A
684
B
$$-$$ 171
C
171
D
$$-$$ 342
4
WB JEE 2016
MCQ (Single Correct Answer)
+1
-0.25
$$1 + {}^n{C_1}\cos \theta + {}^n{C_2}\cos 2\theta + ... + {}^n{C_n}\cos n\theta $$ equals
A
$${\left( {2\cos {\theta \over 2}} \right)^n}\cos {{n\theta } \over 2}$$
B
$$2{\cos ^2}{{n\theta } \over 2}$$
C
$$2{\cos ^{2n}}{\theta \over 2}$$
D
$${\left( {2{{\cos }^2}{\theta \over 2}} \right)^n}$$
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