Question 959687
{{{y=ax^2+bx+c}}}
So then using the points,
{{{-20=a(-2)^2+b(-2)+c}}}
1.{{{4a-2b+c=-20}}}
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{{{-4=a(0)^2+b(0)+c}}}
2.{{{c=-4}}}
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{{{-20=a(4)^2+b(4)+c}}}
3.{{{16a+4b+c=-20}}}
Substitute for {{{c}}} in eq. 1 and eq. 3.
{{{4a-2b-4=-20}}}
{{{4a-2b=-16}}}
4.{{{2a-b=-8}}}
and
{{{16a+4b-4=-20}}}
{{{16a+4b=-16}}}
5.{{{4a+b=-4}}}
Add eq. 4 and 5,
{{{2a-b+4a+b=-8-4}}}
{{{6a=-12}}}
{{{a=-2}}}
Then from eq. 5,
{{{4(-2)+b=-4}}}
{{{-8+b=-4}}}
{{{b=4}}}
So,
{{{y=-2x^2+4x-4}}}
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{{{drawing(300,300,-10,10,-25,5,grid(1),circle(-2,-20,0.3),circle(0,-4,0.3),circle(4,-20,0.3),graph(300,300,-10,10,-25,5,-2x^2+4x-4))}}}.