Given that we have the function f(x) = 5x-√8, it is equal to 13 at some value of x. This relation can be written in equation as
Move √8 to the other side of the equation so that only the term with x will be left on the left-hand side. We have
Divide both sides by 5, we get
The square root of 8 can be further simplified as
Hence, the value of x can also be rewritten as
Thus, the value of x to satisfy f(x) = 13 when f(x)=5x -√8 is