分解因式:2x^2-xy-6y^2+7x+7y+3

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分解因式:2x^2-xy-6y^2+7x+7y+3

分解因式:2x^2-xy-6y^2+7x+7y+3
分解因式:2x^2-xy-6y^2+7x+7y+3

分解因式:2x^2-xy-6y^2+7x+7y+3
待定系数法的经典例子
2x^2-xy-6y^2+7x+7y+3
=(x-2y+m)(2x+3y+n)
=2x^2-xy-6y^2+(2m+n)x+(3m-2n)y+mn
2m+n=7
3m-2n=7
mn=3
m=3
n=1
所以
原式=(x-2y+3)(2x+3y+1)

2x^2-xy-6y^2+7x+7y+3
=2x^2+(7x-xy)-(6y^2-7y-3)
=2x^2+(7-y)x-(3y+1)(2y-3)
=(2x+3y+1)(x-2y+3)