Stationary Point – How to Find and Classify the Stationary Points of $y = \frac{x^2}{x-4}$

Question

I have already obtained the answer by using the quotient rule and so there are stationary points at x = 0 and x = 8. I am fine at doing these types of questions but I don't fully understand the meaning behind the answer. This was also provided in the solution of the answer

Now y approaches infinity as x approaches infinity, and
y approaches infinity as x approaches 4^(+). Hence, x = 8 must be a minimum. Similarly, y approaches (-)infinity as x approaches (-)infinity
and as x approaches 4^(-). Hence x = 0 is a maximum.

How do you know that x=8 is a maximum and x=0 is a minimum also what does the 4^(+) and 4^(-) mean ? sorry if this is a silly question I just don't get what the final answer says.

Answer 1

Take the second derivatives to determine whether a function is maximized or minimized at a point.

$4^+$ means approaching the point $4$ from above.