Σ 2" +3 = 36 33. 3n

To show that $\sum _{n=-1}^{\infty }\frac{2^{n+3}}{3^n}=36$

Let $a,ar,a{r}^2,a{r}^3...$be an infinite G.P.

Then the sum of infinite G.P. is given by:

$S=\frac{a}{1-r}$ where $a$ is the first term and $r$ is common ratio