由p=0.638,r=10.代入，得d3-30d2+2552=0 令fx)=x3-30x2+2552,函数图形如下所示 3000 2000 1000 0 -1000 -2000 0 5 10 15 20 8/148/14 0 5 10 15 20 -2000 -1000 0 1000 2000 3000 由 =0.638, r = 10.代入,得d 3 – 30 d 2 + 2552 = 0 令 f (x) = x 3 – 30 x 2 + 2552 ,函数图形如下所示