All of given options contain quadratic functions. One way to determine the extreme value is squaring the expression with variable x.
Option B contain the expression where you can see perfect square. Thus, equation (choice B) reveals its extreme value without needing to be altered.
To determine the extreme value of this equation, you should substitute x=2 (x-value that makes expression in brackets equal to zero) into the function notation:
The extreme value of this equation has a minimum at the point (2,5).