Imagine a machine that you put number into. However, the machine has a function that creates a new number. Remember that the number that comes out depends on the number that is put in. With this information, i'm pretty sure its the third bubble. im sorry that my information might not be accurate.
It's not quadratic. It's linear. Each time x increases by 1, f(x) increases by 4. So the slope is 4. The y-intercept (when x=0) is -12. The equation of the line is therefore:
