Question

Coefficient of x in the expansion of $(x^2+\frac{a}{x}{)}^5$ is

• A.
• B.
• C.
• D.

Answer 1

The correct option is B

$T_{r+1}=5_{c_r}(x^2{)}^{5-r}{\left(\frac{a}{x}\right)}^r=5_{c_r}.a^r.x^{10-3r}\therefore 10-3r=1\Rightarrow r=3\therefore co-efficent=5_{c_3}.a^3=10.a^3$