Put in math terms, the equation we are given is y = 2x² + 28x - 8
This equation is set up in standard form. Standard form is ax² + bx + c. In order to find the vertex, we'll complete the following equation: -b / 2a -28 / 2 (2) -28 / 4 -7
Next, we'll just put -7 into the equation in place of x.
2(-7)² + 28(-7) - 8 2(49) -196 - 8 98 - 204 -106
So the vertex is (-7, -106). Have fun plotting that.
The histogram will have a horizontal or an x axis of time/minute intervals of the calls (5 minutes in each), and the vertical axis or y axis will be the number of calls made.