Expression evaluation

Question

I have encountered this expression and I cannot evaluate to the desired result on the right side

$$3\cdot4^{k+1}+4^{k+1}-64 = 4^{k+2}-64$$

Answer 1

$3\cdot 4^{k+1}+4^{k+1}=(3+1)4^{k+1}=4\cdot 4^{k+1}=4^{k+2}$.

Answer 2

$$3\cdot 4^{k+1}+4^{4+1}=4^{k+1}+4^{k+1}+4^{k+1}+4^{k+1}=4\cdot 4^{k+1}$$

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

Answer 3

$$3\cdot4^{k+1}+4^{k+1}-64 = (4^{k+1}\cdot(3+1)) - 64 =(4^{k+1}\cdot 4^{1}) - 64 = 4^{k+2} - 64 $$