∵X²+3XY+2Y²=(x+2y)(x+y) ∴可用待定系数法分解 令：X²+3XY+2Y²-Y-1=(x+2y+A)(x+y+B) 则有：X²+3XY+2Y²-Y-1 =(x+2y+A)(x+y+B) =X²+3XY+2Y²+（A+B）x+(A+2B)y+AB 比较等式...