Question

What is the equation of the parabola that has its vertex at (8,-1) and a y-intercept of (0,-17)?

Answer 1

y = a(x + 1.5)^2 - 12.5

y intercept is (0,-8) so:-

-8 = a(0+1.5)^2 - 12.5

-8 = 2.25a - 12.5

a = 4.5/ 2.25 = 2

so we have

y = 2 ( x +1.5)^2 - 12.5

solving for x when y = 0:-

(x + 1.5)^2 = 12.5/2 = 6.25

taking sqrt's x + 1.5 = +/- 2.5

x = -4, 1

so the x intercepts are (-4,0) and (1,0)

Answer 2

y = –1∕4(x – 8)^2 – 1

Explanation:

I took the exam and got it right.