Question:
If the co-efficient of $x^{7}$ and $x^{8}$ in the expansion of $\left(2+\frac{x}{3}\right)^{n}$ are equal, then the value of $n$ is equal to________.
Solution:
${ }^{n} C_{7} 2^{n-7} \frac{1}{3^{7}}={ }^{n} C_{8} 2^{n-8} \frac{1}{3^{8}}$
$\Rightarrow \mathrm{n}-7=48 \Rightarrow \mathrm{n}=55$
Click here to get exam-ready with eSaral
For making your preparation journey smoother of JEE, NEET and Class 8 to 10, grab our app now.