关键“齐二次的分解”2x^2+3xy+y^2＝（2x+y)(x+y)设[(2x+y)+n][(x+y)+M]=（2x+y)(x+y)+n(x+y)+m(2x+y)+mn=（2x+y)(x+y)+(n+2m)+(n+m)y+mn对比系数得n+2m=-4且m+n=-3且mn=2n＝－2,m＝－1原式＝（2x+y-2)(x+y-1)...