Question 366152
Use the general form of a quadratic equation.
{{{y=ax^2+bx+c}}}
{{{7=a(2)^2+b(2)+c}}}
1.{{{highlight(4a+2b+c=7)}}}
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{{{2=a(3)^2+b(3)+c}}}
2.{{{highlight(9a+3b+c=2)}}}
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{{{4=a(5)^2+b(5)+c}}}
3.{{{highlight(25a+5b+c=4)}}}
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Now you have three linear equations in three unknowns (a,b,c).
Solve using any method (substitution, elimination, matrix methods). 
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{{{drawing(300,300,-2,10,-2,10,
circle(3,2,0.3),circle(5,4,0.3),circle(2,7,0.3),grid(1),graph(300,300,-2,10,-2,10,0))}}}
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It looks like the parabola opens upwards.