Look in attachment ..answer if u know only pls

First of all, you have to understand  is a square-root function. 

Square-root functions are continuous across their entire domain, and their domain is all real x-values for which the expression within the square-root is non-negative. 

In other words, for any square-root function  and any input  in the domain of  (except for its endpoint), we know that this equality holds:   

Let's take  as an example. 

The domain of  is all real numbers such that .  Since   is the endpoint of the domain, the two-sided limit at that point doesn't exist (you can't approach  from the left). 

However, continuity at an endpoint only demands that the one-sided limit is equal to the function's value: 

 

In conclusion, the equality  holds for any square-root function  and any real number   in the domain of  except for its endpoint, where the two-sided limit should be replaced with a one-sided limit. 

The input ,  is within the domain of . 

Therefore, in order to find    we can simply evaluate  at .