Prove that 2n+2 + 32n+1 is divisible by 7 for all integers, n > 0
So far I have:
Let n = 1
23 + 33 = 8 + 27 = 35, which is divisible by 7
Assume true for n = k
2k+2 + 32k+1 = 7M
Consider n = k + 1
2k+3 + 32k+3
= 2k.23 + 32k + 33
= 2k.8 + 9k.27
= 2k.8 + 9.(3.9k)
= 2k.8 +...