What are all of the real roots of the following polynomial? f(x) = x4 - 13x2 + 36

A.
-3, -1, 1, and 3
B.
-3 and 3
C.
-3, -2, 2, and 3
D.
-2 and 2

Lin is writing an equation to model the proportional relationship between y, the total cost in dollars of downloading videos from a website, and x, the number of videos downloaded. she knows that the total cost to download 3 videos was $12. her work to find the equation is shown below. joylin’s work step 1 k= 3/12= 0.25 step 2 y= 0.25x where did joylin make her first error?