Expression evaluation I have encountered this expression and I cannot evaluate to the desired result on the right side
$$3\cdot4^{k+1}+4^{k+1}-64 = 4^{k+2}-64$$

$$3\cdot 4^{k+1}+4^{4+1}=4^{k+1}+4^{k+1}+4^{k+1}+4^{k+1}=4\cdot 4^{k+1}$$
Or a quicker way: $$3\cdot 4^{k+1}+4^{k+1}=4^{k+1}\cdot(3+1)=4^{k+1}\cdot 4.$$
