Recall that if x $=$ a $+$ bi and y $=$ c $+$ di are two complex numbers, then their product is xy $=($ac $$ bd$)+($ad $+$ bc$)$i$,$ where i$^2=1$ is the square root of unit. Note that by definition we need $4$ real$-$number multiplications $($namely ac$,$ bd$,$ ad and bc$).$ Can you find a way to perform complex number multiplication using only $3$ real$-$number multiplications?