用待定系数法分解因式,x2+2xy+y2+x+y-2x2+xy-2y2+2x+7x-32a2-7ab-22b2-5a+35b-3字母后面的数代表指数

Question

用待定系数法分解因式,x2+2xy+y2+x+y-2 x2+xy-2y2+2x+7x-3 2a2-7ab-22b2-5a+35b-3
字母后面的数代表指数

Answer 1

x2+2xy+y2+x+y-2=(x+y+a)(x+y+b)=x2+2xy+y2+(a+b)(x+y)+ab
所以(a+b)=1,ab=-2,
a=2,b=-1或者a=-1,b=2
x2+xy-2y2+2x+7x-3=(x+2y)(x-y)+2x+7x-3=(x+2y+a)(x-y+b)
和上题一样.
2a2-7ab-22b2-5a+35b-3=(2a-11b)(a+2b)-5a+35b-3=(2a-11b+m)(a+2b+n)
和上题一样.