如何将y = pow（x，z）反转为x？

Question

据我所知，没有内置函数可以直接执行此操作，所以log（）？或者简单的数学快捷方式，如：

2017-01-22 10:04:48.867 xxx[5404:1574257] start Load WebView

2017-01-22 10:04:48.868 xxx[5404:1584402] myQueue

2017-01-22 10:04:48.868 xxx[5404:1574257] viewLodLoad

2017-01-22 10:04:48.946 xxx[5404:1574257] mainQueue

2017-01-22 10:05:01.547 xxx[5404:1574257] decidePolicyForNavigationAction    

2017-01-22 10:05:01.548 xxx[5404:1574257] didStartProvisionalNavigation

2017-01-22 10:05:02.468 xxx[5404:1574257] decidePolicyForNavigationResponse 

X

Answer 1

如果y=pow(x,z)然后x = pow(y,1.0/z)：

>>> y = pow(3,1.7)
>>> y
6.473007839923779
>>> pow(y,1.0/1.7)
3.0