Question

If the thrid term in the binomial expansion of $(1+x{)}^m$ is - $\frac{1}{8}$$x^2$, then the rational value of m is

• A. 2
• B. 1/2
• C. 3
• D. 4

Answer 1

The correct option is B

1/2

$M_{c_2}=-\frac{1}{8}\Rightarrow \frac{M(M-1)}{2}=-\frac{1}{8}\Rightarrow 4m^2-4m+1=0\Rightarrow (2m-1{)}^2=0\Rightarrow M=\frac{1}{2}$