x-y=1,求x²-y²-2y

来源：学生作业帮助网编辑：作业帮时间：2024/05/07 08:47:53

x-y=1,求x²-y²-2y
x-y=1,求x²-y²-2y

x-y=1,求x²-y²-2y
x-y=1
所以原式=(x+y)(x-y)-2y
=(x+y)*1-2y
=x+y-2y
=x-y
=1

x=y+1 替换为 (y+1)² -y²-2y
y²+2y+1-y²-2y = 1