Quadratic functions take the shape of a parabola. The parabola can either have a minimum value or a maximum value.
Exponential functions are either continuously growing or receding. The difference from a linear function is that the growth/decay increases/decreases as you move in the positive horizontal direction.
Let's show a few examples of these types of graphs.
From the exercise, the description says that the population of bacteria doubles every 20 minutes. If something doubles in even intervals, it's going to increase continuously faster. This means the population increases exponentially.
b From the exercise, we know that Avery is able to finish 3 problems every 5 minutes which gives her a rate of 35=0.6 problems per minute. Since her rate is constant, the graph that describes this must be a linear function.
c When something is launched into the air, gravity will make the trajectory resemble a parabola. Therefore, a quadratic function would describe the path of the apple best.
