1.
5(7m+n)^3-3(7m+n)^2+3(7m+n)+1=0 (mod 7), n=0~6
5n^3-3n^2+3n+1=0 (mod 7)
使用排除法。结果是n=2。
因此 x = 2 + 7m, (m是任意整数)
2.
7^125 mod(41)
=7 X (7 X 7)^62 mod(41)=7 X 8^62 mod(41)
= 14 X 32^37 mod(41) = 14 X(-9)^37 mod(41)
= -14X9 X 9^36 mod(41) = -3 X 81^18 mod(41)
= -3 X(-1)^18 mod(41)= -3 mod(41) = 38