Answer:
f(x) = y
Explanation:
Think of it as a input-output function machine, where you give a number as input to the machine, and the you get a number as the output from the machine. The input is x which goes inside of the ( )'s, and the output is f(x). The output 'f(x)' is sometimes called the y-value because y = f(x).
For example f(-2) = 4. The number you give to the machine is -2 since it's the x-value and the number is in ( )'s. The output number the machine gives back to you is 4, which is the y-value.
Hope this helps!