Remember, to be a function, all elements in the domain should correspond to one element in the range.
The domain is the x coordinate, range is the y coordinate.
The domain we can solve for as the set {4.2, 5, 7}. The range is the set {0, 1.5, 2.2, 4.8}.
But we see that an element in the domain corresponds to more than one element in the range, thus making it not a function.