Solve the equation x2 − 100 = 0. x = 0, -10 x = 0, 10 x = 10, -10 x = 50, -50

(x² - 100) = 0 is a difference of two squares. If you factor it, you get (x - 10)(x + 10) = 0

Set each equation equal to zero.

x - 10 = 0
x = 0 + 10
x = 10

x + 10 = 0
x = 0 - 10
x = - 10

So x = - 10, 10. Your third option is your answer. 

There is no graph but if you’re making one you can make a line graph with words on x axis and minutes on y axis with two different color lines showing student one and student two or you can make a bar graph with student 1 and student 2 on bottle on either side of the graph and have words per minute on the y axis