Solve for x x middot 731 13 4 mod 11SolutionBy Fermats Lit
Solve for x: x middot 7^31 +- 13 = 4 (mod 11).
Solution
By Fermat\'s Little Theorem
7^{10}=1 mod 11
7^{30}=(7^{10})^3=1 mod 11
7^{31}=7 mod 11
HEnce
x.7^{31}+13=4 mod 11 , becomes
7x+13=4 mod 11
7x+2=4 mod 11
7x=2 mod 11
7*8=56=55+1=1 mod 11
So we multiply by 8 and get
56x=16=5 mod 11
x=5 mod 11
