3x+4xy-y =3(x+ xy×4/3 - y×1/3) =3[(x+ 2×2/3 ×xy +4/9y) - y/3- 4/9y] =3[(x+2/3y) - 7/9 y] =3(x+2/3y +√7/3y)(x+2/3y - √7/3y) =3[x+(2+√7)/3y][x+(2-√7)/3y] 追问：是否可以继续分解呢?回答：方程3x^2+4x-1=0的根是x=(-2±√7)/3 所以原式=(x+2y/3+√7y/3)(x+2y/3-√7y/3)
3x+4xy-y =3(x+ xy×4/3 - y×1/3) =3[(x+ 2×2/3 ×xy +4/9y) - y/3- 4/9y] =3[(x+2/3y) - 7/9 y] =3(x+2/3y +√7/3y)(x+2/3y - √7/3y) =3[x+(2+√7)/3y][x+(2-√7)/3y] 追问：是否可以继续分解呢?回答：方程3x^2+4x-1=0的根是x=(-2±√7)/3 所以原式=(x+2y/3+√7y/3)(x+2y/3-√7y/3)