Find the remainder when (1+8)n+7 is divided by 8
(1+8)n+7 = (nC0(8)n+nC1(8)n−1+nC2(8)n−2............+nCn−1(8)1+nCn)+7
(1+8)n+7 = (nC0(8)n+nC1(8)n−1+nC2(8)n−2............+nCn−1(8)1+1)+7
(1+8)n+7 = (nC0(8)n+nC1(8)n−1+nC2(8)n−2............+nCn−1(8)1+8
= 8k
So the remainder will be 0