1.(x-y)(x+y)+(x-y)+(x+y)

题目

1.(x-y)(x+y)+(x-y)+(x+y)
2.x(x+2)-(x+1)(x-1),其中x=-二分之一
请写清步骤,结果.

答案

1.(x-y)(x+y)+(x-y)+(x+y)=x²-y²+x²-y²=2x²-2y²2.x(x+2)-(x+1)(x-1)=x²+2x—（x²-1）=x²+2x-x²+1=2x+1=2×1/2+1=2