Question

先去括号,再合并同类项：第一题-(2x-3y)+(-x+2y)第二题a的平方-2（ab-b的平方）-b的平方第三题（x的

Answer 1

-(2x-3y)+(-x+2y)

=-2x+3y-x+2y

=-3x+5y

a²-2(ab-b²)-b²

=a²-2ab+2b²-b²

=a²-2ab+b²

=(a-b)²

(x²-y²)-3(2x²-3y²)

=x²-y²-6x²+9y²

=-5x²+8y²