Question

Find the largest prime divisor of $15^6 - 7^6$.

Answer 1

ANS : 11,272,976 = 2^4 * 11 * 13^2 * 379

Step by step :

[7 + b]^6 - 7^6

b^6 + 42 b^5 + 735 b^4 + 6860 b^3 + 36015 b^2 + 100842 b + 117649 -7^6

Sub 8 for b

262,144 + 1,376,256 + 3,010,560 + 3,512,320 + 2,304,960 + 806,736

11,272,976 = 2^4 * 11 * 13^2 * 379