Question

Найти остаток от деления числа а на m
a=15^254 (mod)19

Answer 1

$15^{254}=\equiv (-4)^{2*127}(mod\:19)=16^{127}\equiv(-3)^{127}(mod\:19)=-27*(-3)^{4*31}=(-27)*81^{31}\equiv (-8)*5^{31}(mod\:19)=(-40)*25^{15}\equiv(-2)*6^{15}(mod\:19)=(-12)*36^7\equiv 7*(-2)^7(mod\:19)=(-7)*16*8\equiv (-7)*(-3)*8(mod\:19)=21*8\equiv 16(mod\:19)$