2x^2-3xy-y^2=0x=(3+√17)y/4x=(3-√17)y/4所以2x^2-3xy-y^2=[x-(3+√17)y/4][x-(3-√17)y/4]
十字相乘法分解因式2x^2-3xy-y^2 =(2x-y)(x+y)
2x^2-3xy-y^2=(2x-y)(x+y)
