Question

If the number of terms in the expansion $(2x+y{)}^n-(2x-y{)}^n$ is 8, then the value of n is ........... (where n is odd ).

• A. 17
• B. 19
• C. 15
• D. 13

Answer 1

The correct option is C 15

The number of terms in the expansion $(x+y{)}^n-(x-y{)}^n$ is $\frac{n+1}{2}$, when n is odd.

The given number of terms = 8

$\frac{n+1}{2}=8$

$n+1=16$

$n=15$