设2x²-5x-1=y
2x²-5x+ (2x²-5x+1)分之8-5=0
2x²-5x+1+ (2x²-5x+1)分之8-6=0
y+（8/y）-6=0
y²+8-6y=0
(y-2)(y-4)=0
y1=2 y2=4
2x²-5x-1=2或
2x²-5x-1=4