Question

计算：①（a-b）（a-2b-1）②（x-y+1）（x-y-3

计算：①（a-b）（a-2b-1）②（x-y+1）（x-y-3）

Answer 1

①原式=a²-2ab-a-ab+2b²+b
=a²-3ab+2b²-a+b；

②原式=x²-xy-3x-xy+y²+3y+x-y-3
=x²-2xy+y²-2x+2y-3．