已知x2+x+3=0,求x5+3x4+2x3+2x2-10x的值.
1个回答

解题思路:要先提公因式,再根据x2+x+3=0得出x2+x=-3分别一步步代入,即可求出答案;

∵x2+x+3=0,

∴x2+x=-3,

x5+3x4+2x3+2x2-10x

=x3(x2+x)+2x4+2x3+2x2-10x

=-3x3+2x4+2x3+2x2-10x

=2x4-x3+2x2-10x

=2x2(x2+x)-3x3+2x2-10x

=-3x3-4x2-10x

=-3x(x2+x)-x2-10x

=9x-x2-10x

=-x2-x

=-(x2+x)

=3.

点评:

本题考点: 因式分解的应用.

考点点评: 此题考查了因式分解的应用;解题的关键先提取公因式后进行分解,再把x2+x=-3代入即可,解题时要细心.