Question 1073022
Complete the square to get the function into vertex form,
{{{y=-x^2+4x}}}
{{{y=-(x^2-4x)}}}
{{{y=-(x^2-4x+4)+4}}}
{{{y=-(x-2)^2+4}}}
So the vertex is,
(2,4)
So then using the vertex form,
{{{-(x-2)^2+4=0}}}
{{{(x-2)^2=4}}}
{{{x-2=0 +- 2}}}
{{{x=2 +- 2}}}
{{{x=4}}} and {{{x=0}}}
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*[illustration fr32.JPG].