5x²-3x-5=0等式两边同除以5xx -3/5 -1/x=0x- 1/x=3/55x²-3x-5=05x-2x-5=x5x²-2x- 1/(5x²-2x-5)=5x²-2x -5 -1/(5x²-2x-5) +5=x -1/x +5=3/5 +5=28/5x²+ 1/x²=(x-1/x)²+...