Question

已知x-y=3,求代数式7-x+y-(x-y)²的值.

Answer 1

7-x+y-(x-y)²=7-（x-y）-(x-y)²=7-3-3^2=4-9= -5

Answer 2

7-x+y-(x-y)²=7-(x-y)-(x-y)平方=7-3-9=-5
把数带进去，换一下格式就行了，很简单的。