(x+2)(x-2)+y(4-y)=x²-4+4y-y²=x²-(y-2)²=(x+y-2)(x-y+2)
展开 分解
(x+2)(x-2)+y(4-y)=x2-4+4y-y2=x2-(y2-4y+4)=x2-(y-2)2=(x+y-2)(x-y+2)
