首先要先证得：整数A的平方,被4除的余数仅可能为0或1.因：A仅可能为奇数或偶数.当A为偶数时,令A = 2N.A^2 = (2N)^2 = 4N^2 ,被4除余0.当A为奇数时,令A = 2N + 1.A^2 = (2N + 1)^2 = 4N^2 + 4N + 1 = 4(N^2 + N) + 1,...