令x=√n,则x ≥ 0.原式化为：5x²+x-500=0,解得x=(-1+√10001)/10 或(-1-√10001)/10（舍,因为与x≥0不符）则n=x²=[(-1+√10001)/10]² = (10002-2√10001)/100=100.02-0.02√10001...