5x²－3x－5＝0∴5x²－2x－5＝x∴5x²－2x－[1÷（5x²－2x－5）]=x+5-1/x=(x²+5x-1)/x=5(x²+5x-1)/5x=(5x²+25x-5)/5x=(5x²-3x-5+28x)/5x=28/5