0 c=1.5 a=1 b=2
1 c=1.25 a=1 b=1.5
2 c=1.375 a=1.25 b=1.5
3 c=1.3125 a=1.25 b=1.375
4 c=1.34375 a=1.3125 b=1.375
5 c=1.328125 a=1.3125 b=1.34375
6 c=1.3203125 a=1.3125 b=1.328125
7 c=1.32421875 a=1.3203125 b=1.328125
8 c=1.326171875 a=1.32421875 b=1.328125
9 c=1.3251953125 a=1.32421875 b=1.326171875
10 c=1.32470703125 a=1.32421875 b=1.3251953125
11 c=1.324951171875 a=1.32470703125 b=1.3251953125
12 c=1.3248291015625 a=1.32470703125 b=1.324951171875
13 c=1.3247680664062 a=1.32470703125 b=1.3248291015625
14 c=1.3247375488281 a=1.32470703125 b=1.3247680664062
15 c=1.3247222900391 a=1.32470703125 b=1.3247375488281
16 c=1.3247146606445 a=1.32470703125 b=1.3247222900391
17 c=1.3247184753418 a=1.3247146606445 b=1.3247222900391
18 c=1.3247165679932 a=1.3247146606445 b=1.3247184753418
19 c=1.3247175216675 a=1.3247165679932 b=1.3247184753418
20 c=1.3247179985046 a=1.3247175216675 b=1.3247184753418
after 20 steps, root is 1.3247179985046387 with error 9.5e-07, f=1.8e-07
