初二數學因式分解已知x-y+1的絕對值與xx+8x+16互為相反數,求xx+2xy+yy的值
xx+8x+16=(x+4)^2>=0
x-y+1的絕對值>=0
所以xx+8x+16=(x+4)^2=0
x=-4
y=-3
xx+2xy+yy=49
12a(xx+yy)-18b(xx+yy)該如何因式分解
(12a-18b)(xx+yy)
=6(2a-3b)(xx+yy)
xx-yy-x-y因式分解
xx-yy-x-y =(x^2-y^2)-(x+y)=(x+y)(x-y)-(x+y)=(x+y)(x-y-1)