99 Percentile Qs Bank for JEE MainMathematicsBinomial Theorem
The coefficient of x n in the polynomial ( x + 2 n + 1 C 0 ) ( x + 2 n + 1 C 1 ) ( x + 2 n + 1 C 2 ) ..... ( x + 2 n + 1 C n ) is
Options
- A2 n + 1
- B2 2 n + 1 − 1
- C2 2 n − 1
- D2 2 n
Correct answer
D. 2 2 n
Step-by-step solution
Given Expression is, ( x + 2 n + 1 C 0 ) ( x + 2 n + 1 C 1 ) ( x + 2 n + 1 C 2 ) ..... ( x + 2 n + 1 C n ) If P is coefficient of x n then, P = 2 n + 1 C 0 + 2 n + 1 C 1 + 2 n + 1 C 2 + ..... + 2 n + 1 C n -------(1) ⇒ P = 2 n + 1 C 2 n + 1 + 2 n + 1 C 2 n + 2 n + 1 C 2 n − 1 + ..... + 2 n + 1 C n + 1 ------(2) ( ∵ n C r = n C n − r ) adding (1) and (2) 2 P = ( 2 n + 1 C 0 + 2 n + 1 C 1 + ....... + 2 n + 1 C 2 n + 1 ) 2 P = 2 2 n + 1 ∴ P = 2 2 n