x=(√5-1)/2
2x+1=√5
两边平方
4x²+4x+1=5
x²=1-x
所以x⁴=(1-x)²
=x²-2x+1
所以原式=x²-2x+1+x²+2x-1
=2x²
=2(1-x)
=2-2x
=2-(√5-1)
=3-√5