Concept:The total number of terms in the binomial expansion of (a + b)n is n + 1, i.e.one more than the exponent n.Calculation:\(\left(1 + \frac{2}{x}\right)^9\left(1-\frac{2}{x}\right)^9\) can be written as ? \(\left[\left(1 + \frac{2}{x}\right)\left(1-\frac{2}{x}\right)\right]^9\)We know that, (a + b)(a - b) = a2 - b2?\(\left[1-\left(\frac{2}{x}\right)^2\right]^9 \)? Total number of the terms = 9 + 1 = 10? There are 10 terms in the expansion of \(\left(1 + \frac{2}{x}\right)^9\left(1-\frac{2}{x}\right)^9.\)