First let's clarify the terminology. If f is a function from set X to set Y then X is thedomainand Y is thecodomain. The set f(X) = {f(x) : x in X} of values actually taken by X is theimage. Unfortunately the terminology is not completely fixed and the codomain is also called the target or range and the image is also called the range by some authors. In your case you want the image. The domain is the four-element set {-4,-2,0,4}, the codomain is the real numbers. The range is the set of actual values taken, namely {f(-4), f(-2), f(0), f(4)}. You need to compute these and then write the set of those values. (Notice that if a value is taken more than once it only appears once in the set)