SOLUTION: What is the x-intercept of a parabola with the vertex (-1,80) and the y intercept (0,75)

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Question 698729: What is the x-intercept of a parabola with the vertex (-1,80) and the y intercept (0,75)
Answer by Positive_EV(69) About Me  (Show Source):
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Since this parabola has only one y-intercept, it must open either up or down. A parabola that opens up or down can be written in the form y+-+k+=+a%2A%28x-h%29%5E2. In this form, the vertex is (h, k). So to start, plug in those values:

y+-+80+=+a%2A%28x%2B1%29%5E2

To find a, plug the point of the y-intercept into this equation:

75+-+80+=+a%2A%280%2B1%29%5E2
-5+=+a
y+-+80+=+-5%2A%28x%2B1%29%5E2

You can find the x-intercepts (there will be two of them) by setting y = 0 and solving for x:

-80+=+-5%2A%28x%2B1%29%5E2
16+=+%28x%2B1%29%5E2
4+=+%28x%2B1%29 or -4+=+%28x%2B1%29
So x = 3 or x = -5. The x-intercepts are thus (3,0) and (-5,0).