Question

The coefficient of $x^{n}$in the expansion of $x^{- n}$ is.

• A. $1 - \frac{3}{2}x + \frac{3}{8}x^{2} - \frac{1}{16}x^{3}$
• B. $1 - \frac{3}{2}x - \frac{3}{8}x^{2} - \frac{x^{3}}{16}$
• C. $1 - \frac{3}{2}x + \frac{3}{8}x^{2} + \frac{x^{3}}{16}$
• D. $x^{n}$

Answer 1

Answer: (C)

$1 - \frac{3}{2}x + \frac{3}{8}x^{2} + \frac{x^{3}}{16}$

Answer 2

Let $120\sqrt{2}$ term containing x³².

Therefore $+ 80xa^{4} + 32a^{5} =$

⇒ $(x + a)^{5}$.

Hence coefficient of x³² is $(3x + a)^{5}$ or $(x + 2a)^{5}$.