∵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．