Question 982450
First focus on f(2) = 5



{{{f(x)=ax^2+b}}}



{{{f(2)=a(2)^2+b}}} Plug in x = 2



{{{f(2)=4a+b}}}



{{{5=4a+b}}} Replace f(2) with 5



{{{5-4a=b}}}



{{{b=5-4a}}}



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Now move onto f(3) = 20



{{{f(x)=ax^2+b}}}



{{{f(3)=a(3)^2+b}}} Replace every x with 3



{{{f(3)=9a+b}}}



{{{20=9a+b}}} Replace f(3) with 20



{{{20=9a+5-4a}}} Replace b with 5-4a



I'll let you finish up. The goal is to isolate 'a'. Once you know the value of 'a', you plug it into {{{b=5-4a}}} to find the value of 'b'.