i have a simple question.
can someone please tell me how to get there?
I just dont get it.
$\displaystyle \sum_{j= 0}^\infty \left(0.9\right)^{2j}= \sum_{j=0}^\infty \left(0.9^2\right)^j= \sum_{j= 0}^\infty \left(0.81\right)^j$
is a geometric series with a= 1 and r= 0.81. Use the formula for the sum of a geometric series:$\displaystyle \sum_{j=0}^\infty ar^j= \frac{a}{1- r}$