Summation series for a $\times$ b^x

Question

I know theres a summation series for basic $a^x$. Like $2^{x-1}$ is summed by $2^x-1$. Then how would you sum $5\times2^{x-1}$?

Answer 1

You would distribute out the $5$ and get $$\sum_{i=1}^x 5\cdot 2^{i-1}=5\sum_{1=1}^x 2^{i-1}=5( 2^x-1)$$