题目

我为了快点写完作业并且绝大对,只能这样了,请回答下,硪去写作文先,半小时后就来.
（a-b-3)（a-b+3)
(2x+y+1)(2x+y-1)
(x-2)(x+2)-(x+1)(x-3)
(ab+1)^2-(ab-1)^2
(2x-y)^2-4(x-y)(x+2y)

提问时间：2021-10-27

答案

(1).(2x+y+1)(2x+y-1)
=(2x+y)²-1
=4x²+4xy+y²-1
(2) .(x-2)(x+2)-(x+1)(x-3)
=x²-4-(x²-2x-3)
=2x-1
(3) .(ab+1)^2-(ab-1)^2
=(ab+1+ab-1)(ab+1-ab+1)
=2ab*2
=4ab
望采纳追问(2x-y)^2-4(x-y)(x+2y)回答(2x-y)²-4(x-y)(x+2y)
=4x²-4xy+y²-(4x-4y)(x+2y)
=4x²-4xy+y²-4x²-8xy+4xy+8y²
=-8xy+9y²