Question 350651
Look up "Vertex form" in the Index.
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Use the vertex form of a parabola, {{{y=a(x-h)^2+k}}}
{{{y=a(x-5)^2+3}}}
Now use the point (7,-1) to solve for {{{a}}}.
{{{-1=a(7-5)^2+3}}}
{{{a(4)+3=-1}}}
I leave it to you to complete the solution for {{{a}}}. 
Then plug that into your equation.