Question 1074270
{{{y=-x^2+8x-20}}}


{{{y=-(x^2-8x+20)}}}

{{{-(x^2-8x+16-16+20)}}}

{{{-((x-4)^2+20-16)}}}

{{{-((x-4)^2+4)}}}


{{{highlight(y=-(x-4)^2-4)}}}




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Term for completing the square,  {{{(-8/2)^2=16}}}