单选题
已知方程x3+2x2-5x-6＝0的根为x1＝-1，x2，x3，则
＝( )．
＝( )．
【正确答案】
A
【答案解析】[解析] 设f(x)＝x3+2x2-5x-6，则
f(x)=(x+1)(x-x2)(x-x3)
=x3+(1-x2-x3)x2+(x2x3-x2-x3)x+x2x3
=x3+2x2-5x-6
对比同次项系数，得
[*]
f(x)=(x+1)(x-x2)(x-x3)
=x3+(1-x2-x3)x2+(x2x3-x2-x3)x+x2x3
=x3+2x2-5x-6
对比同次项系数，得
[*]