Question 305899
Use the vertex form.
{{{y=a(x-h)^2+k}}}
where (h,k) is the vertex.
{{{y=a(x-2)^2-1}}}
Now use the point (0,5) to solve for a.
{{{5=a(0-2)^2-1}}}
{{{5=4a-1}}}
{{{4a=6}}}
{{{a=6/4=3/2}}}
{{{highlight(y=(3/2)(x-2)^2-1)}}}
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{{{drawing(300,300,-2,6,-2,6,grid(1),circle(2,-1,.2),green(line(2,-10,2,10)),graph(300,300,-2,6,-2,6,(3/2)(x-2)^2-1))}}}