$\displaystyle \sum i \binom{n}{i}=n2^{n-1}$

The summation is from i=0 to n but I couldnt figure out how to put that in with latex.

I tried expanding out the Left Side but that didn't lead me anywhere.

I thought about splitting the right side's 2 into a form of (x+y)^n but I couldn't figure out what my x and y should be.

Help please?