Question 369008
The equation is in vertex form, {{{y=a(x-h)^2+k}}}
The function max or min occurs at the vertex and equals k.
The max of min is determined by {{{a}}}.
If {{{a>0}}}, then {{{k}}} is the minimum.
If {{{a<0}}}, then {{{k}}} is the maximum.
In this case, {{{a=-1}}}, so 
{{{k=-3}}} is the function maximum.
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{{{drawing(300,300,-10,2,-10,2,grid(1),circle(-5,-3,0.3),blue(line(-5,0100,-5,-100)),graph(300,300,-10,2,-10,2,0,-(x+5)^2-3))}}}