$\left(1-\frac{1}{x}\right)^{10}$ এর বিস্তৃতিতে 7ম পদ নির্ণয় কর।

The coefficient of middle term in the expansion of $(1+{x})^{40}$ is

  $\left ( y^{2} - 2 + \frac{1}{y^{2}} \right )^{8}$ এর বিস্তৃতিতে পদ সংখ্যা কত?

The $5$th term in the expansion of $\left(2x^2 + \dfrac{3}{x}\right)^5$ is

If the coefficients of 6th and 5th terms of expansion $(1+x)^n$ ;are in the ratio 7:5, then find the value of n.