Question 335604
Convert the equation to vertex form, {{{y=a(x-h)^2+k}}} where (h,k) is the vertex, by completing the square.
{{{y=-5x^2-x+9}}}
{{{y=-5(x^2+(1/5)x)+9}}}
{{{y=-5(x^2+(1/5)x+1/100)+9+5/100}}}
{{{y=-5(x+1/10)^2+181/20}}}
The vertex lies on the axis of symmetry.
{{{highlight(x=-1/10)}}}
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{{{drawing(300,300,-2,2,-2,10,blue(line(-1/10,-10,-1/10,10)),grid(1),graph(300,300,-2,2,-2,10,-5x^2-x+9))}}}