5x²-3x-5=0
则5x²-2x=x+5
5x²-5=3x
x²-1=3x/5
所以5x²-2x-1/(5x²-2x-5)
=x+5-1/(3x-2x)
=(x²+5x-1)/x
=(3x/5+5x)/x
=3/5+5
=28/5