Hello,
[tex]a_0=72\\
a_1=72* \dfrac{1}{2}=36 \\
...\\
a_i=72* \dfrac{1}{2^i} \\\\
\lim_{n \to \infty} \sum_{i=0}^{\infty}\ a_i = \lim_{n \to \infty}72* \sum_{i=0}^{\infty}\ \dfrac{1}{2^i} \\\\
=72* \lim_{n \to \infty} \dfrac{1-\frac{1}{2^{n+1}}}{1-\frac{1}{2}} \\\\
=72*2=144
[/tex]
