Since the function is a straight line with a gradient of 15, there lies no restriction on the value of f(x). For every straight line, unless specified, there would usually be no restriction on the range.
Thus, we can say that the range is: all real values.
More formally written:
[tex]\text{Range of function: } f(x) \in \mathbb{R}[/tex]
The latter section indicates that f(x) is a real number (something that we can visually represent on a number line; the only unreal numbers we have are: imaginary units, often represented as i, which represents the square root of -1)
