Question 698729
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*(x-h)^2}}}. In this form, the vertex is (h, k). So to start, plug in those values:<br>

{{{y - 80 = a*(x+1)^2}}}<br>

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

{{{75 - 80 = a*(0+1)^2}}}
{{{-5 = a}}}
{{{y - 80 = -5*(x+1)^2}}}<br>

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

{{{-80 = -5*(x+1)^2}}}
{{{16 = (x+1)^2}}}
{{{4 = (x+1)}}} or {{{-4 = (x+1)}}}
So x = 3 or x = -5. The x-intercepts are thus (3,0) and (-5,0).