(2x+y+1)(2x+y-1) (x-2)(x+2)-(x+1)(x-3)
=[(2x+y)^2-1](x^2-4)-(x+1)(x-3)
=
好像题目有点问题啊有啊前面四项是相乘吗？第二个括号后面有没有一个+号是 (x-2)(x+2)-(x+1)(x-3)哦，你这里是两个题目啊(2x+y+1)(2x+y-1) =(2x+y)^2-1平方差公式(x-2)(x+2)-(x+1)(x-3) =x^2-4-(x^2-2x-3)=2x-1哦,谢谢啊现在懂了没有啊？