Sathya
Last Activity: 13 Years ago
(7-1)89 + (7+1)89.
This will give
= (89C0789-89C1788+89C2787+...-89C8772+89C8871-89C8970)+(89C0789+89C1788+89C2787+...-89C8772+89C8871-89C8970)
=2*(89C0789+89C2787+89C4785+...+89C8673+89C8871)
89C0789+89C2787+89C4785+...+89C8673 will all be divisible by 49 because they consist of 72 as one of their factor but not 2(89C8871)
Then 2(89C8871)%49 = 21 ---Remainder