(x+y)²-(x²+y²)=?(x+y)²-(x-y)²=?

(x+y)²-(x²+y²)=?(x+y)²-(x-y)²=?
(x+y)²-(x²+y²)=?(x+y)²-(x-y)²=?

(x+y)²-(x²+y²)=?(x+y)²-(x-y)²=?
(x+y)²-(x²+y²)=2xy
(x+y)²-(x-y)²=4xy

2xy 4xy

(x+y)²-(x²+y²)=2xy
(x+y)²-(x-y)²=4xy

x²+2xy+y²-x²-y²=2xy
x²+2xy+y-x²+2xy-y²=4xy

1、原式=x²+2xy+y²-x²-y²
=2xy

2、原式=x²+2xy+y²-(x²-2xy+y²)
=x²+2xy+y²-x²+2xy-y²
=4xy

(x+y)²-(x²+y²)=2xy
(x+y)²-(x-y)²=4xy
\(≧▽≦)/~
PS：~你的采纳是我前进的动力~~

(x+y)²-(x²+y²)
＝(x²+2xy+y²)-(x²+y²)
＝2xy
(x+y)²-(x-y)²
＝(x²+2xy+y²)-(x²-2xy+y²)
＝4xy