Answer:
Reflecting a function over any axis can be complicated if you do not know the proper way to do it, so I am going to use examples to show you.
If f(x)=x is your normal function, then flipping it across the y-axis would look like f(x)=-x.
Explanation:
Placing a - sign before the X will make it flip across the y-axis. After the X, and it flips across the X-axis.