Question

what is the value of ∑_(k=1)^4▒〖(1/4)^k〗

Answer 1

Missing No. ?!

Answer 2

\[
\sum_{k=1}^4\left(\frac 14\right)^k = \left(\frac 14\right)^1+\left(\frac 14\right)^2+\left(\frac 14\right)^3+\left(\frac 14\right)^4
\]Is one way to do it.

Answer 3

You could use \[
\sum_{k=0}^{n-1}r^k =\frac{1-r^n}{1-r}
\]