a (a+b)/2 b x^3+x-1
0 0.5 1 -0.375
0.5 0.75 1 0.17188
0.5 0.625 0.75 -0.1309
0.625 0.6875 0.75 0.01245
0.625
0.65625
0.6875
-0.0611
0.65
a (a+b)/2 b x^3+x-1
0 0.5 1 -0.375
0.5 0.75 1 0.17188
0.5 0.625 0.75 -0.1309
0.625 0.6875 0.75 0.01245
0.625
0.65625
0.6875
-0.0611
0.65