Answer
$f(x)=-(x-2)^2+3$.
Work Step by Step
If the vertex of a graph is at (m,n) then the general formula for the quadratic function is $f(x)=a(x-m)^2+n$. According to the picture the vertex of the graph is at (2,3), hence the quadratic function becomes $f(x)=a(x-2)^2+3$. The point (0,-1) is on the graph, hence if we plug in the values we get $-1=4a+3$, hence a=-1, hence $f(x)=-(x-2)^2+3$.
