Question 1081567
Use the form,
{{{y=ax^2+bx+c}}}
For (-1,-3),
{{{-3=a(-1)^2+b(-1)+c}}}
1.{{{a-b+c=-3}}}
For (1,-2),
{{{-2=a(1)^2+b(1)+c}}}
2.{{{a+b+c=-2}}}
For (2,1),
{{{1=a(2)^2+b(2)+c}}}
3.{{{4a+2b+c=1}}}
Subtract 2 from 1,
{{{a-b+c-a-b-c=-3-(-2)}}}
{{{-2b=-1}}}
{{{b=1/2}}}
Subtract 2 from 3,
{{{4a+2b+c-a-b-c=1-(-2)}}}
{{{3a+b=3}}}
{{{3a+1/2=3}}}
{{{3a=5/2}}}
{{{a=5/6}}}
and finally from 2,
{{{a+b+c=-2}}}
{{{5/6+3/6+c=-12/6}}}
{{{c=-20/6}}}
{{{c=-10/3}}}
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{{{y=(5/6)x^2+x/2-10/3}}}
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*[illustration r2t.JPG].