Question

x的3次方+3x-2=0,则2x的5次方+x的4次方+7x的3次方-x的2次方+x+1的值为

Answer 1

∵x³+3x-2=0,
∴x³=-3x+2
2x⁵+x⁴+7x³-x²+x+1
=2x²(3x-2)+x(3x-2)+7(3x-2)-x²+x+1
=6x³-4x²+3x²-2x+21x-14-x²+x+1
=6x³-2x²+20x-13
=6(-3x+2)-2x²+20x-13
=-18x+12-2x²+20x-13
=-2x²-2x-1
题目有误，最后的结果应不再含有x.