若x=3+1

由x=
3+1得3=（x-1）²，
∴y=2x⁵-4x⁴-x³-6x²-6
=2x³（x²-2x+1）-2x³-x³-6x²-6
=2x³（x-1）²-3x³-6x²-6
=2x³×3-3x³-6x²-6
=3x³-6x²-6
=3x（x²-2x）-6
=3x（x²-2x+1）-3x-6
=3x（x-1）²-3x-6
=3x•3-3x-6
=9x-3x-6
=6x-6
=6（x-1）
=6
3．