If the number of terms in the expansion of
Question:

If the number of terms in the expansion of $\left(1-\frac{2}{x}+\frac{4}{x^{2}}\right)^{n}, x \neq 0$, is 28 , then the sum of the coefficients of all the terms in this expansion, is :-

1. 729

2. 64

3. 2187

4. 243

Correct Option: 1

Solution: