=[2(a-b)]²-(a+b)²=[2(a-b)+(a+b)][2(a-b)-(a+b)]=(3a-b)(a-3b)（x的平方+x+1）的平方-1 =(x²+x+1+1)(x²+x+1-1)=(x²+x+2)(x²+x)=x(x+1)(x²+x+2)
=3a*a+3b*b-10a*b
