KFC math 014讨论，我选Ｄ

014. p, x, y 是integers, 问p^xy的unit digit是否为1?

    (1) p^x的unit digit是1

    (2) p^y的unit digit是1

这题我选Ｄ．

p^xy=(p^x)^y 或(p^y)^x

(1) p^x的unit digit是1，p^xy的unit digit为1

(2) p^y的unit digit是1，p^xy的unit digit为1

所以选Ｄ

is C.

(1) can get Y may negative

(2) can get X may negative

so both can get x , y, are positive integers.

you forget consider Y & X must be positive integers

Y & X may be negative