SOLUTION: Find the x-intercepts of the parabola with vertex (4,-1)and y- intercept (0,15).

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Question 389425: Find the x-intercepts of the parabola with vertex (4,-1)and y- intercept (0,15).
Answer by ewatrrr(24785) About Me  (Show Source):
You can put this solution on YOUR website!


Hi,  

the vertex form of a parabola, y=a%28x-h%29%5E2+%2Bk where(h,k) is the vertex

vertex (4,-1)

y =a(x-4)^2 -1

using y-intercept pt(0,15) to find a

15 = a(-4)^2 - 1

16 = a*16

 1 = a

y = (x-4)^2 - 1  OR y = x^2 - 8x + 15

x^2 - 8x + 15 = 0

factoring

(x-3)(x-5) = 0

(x-3) = 0   x = 3

(x-5) = 0   x = 5

x-intercepts are Pt(3,0) and pt(5,0)