对x,若有y,使得x*y mod 8 等于1，如3*3 mod 8 等于1，则称y为x的倒数，也称为乘法逆元。并非所有的x都有乘法逆元。-Of x, if y, making x* y mod 8 = 1, such as 3* 3 mod 8 = 1, then the reciprocal of y for x, also known as the multiplicative inverse. Not all the x are multiplicative inverse.