Doubt regarding logic formation

#1

Please provide some reference for solving the question. I am not able to find the approach that I could use to solve this question.

#2

We will aplly binary search in this problem. For every possible mid obtained by using binary search we will check of it is the best suitable candidate or not for becoming the Kth root and then we reduce the search space of the binary search according to the mid value. If mid^k is greater than N then we will find the best suitable value from left to mid-1 otherwise we will find much larger value by finding it from mid+1 to right.