![y = ax^2+bx+c \\\\[-0.35em] ~\dotfill\\\\ \stackrel{\textit{using (0 , 0)}}{0 = a(0)^2+b(0)+c}\implies \boxed{0=c} \\\\[-0.35em] ~\dotfill\\\\ \stackrel{\textit{using (-2 , 0)}}{0=a(-2)^2+b(-2)+0}\implies 0=4a-2b\implies 2b=4a \\\\\\ \cfrac{2b}{2}=2a\implies \underline{b=2a} \\\\[-0.35em] ~\dotfill\\\\ \stackrel{\textit{using (2 , 4)}}{4=a(2)^2+b(2)+0}\implies 4=4a+2b\implies \stackrel{\textit{substituting 2b}}{4=4a+2(2a)} \\\\\\ 4=4a+4a\implies 4=8a\implies \cfrac{4}{8}=a\implies \boxed{\cfrac{1}{2}=a}](/tpl/images/2649/4498/7ca8e.png)
![~\dotfill\\\\ \stackrel{\textit{we know that}}{b=2a}\implies b=2\left( \cfrac{1}{2} \right)\implies \boxed{b=1} \\\\[-0.35em] ~\dotfill\\\\ y=\cfrac{1}{2}x^2+1x+0\implies \boxed{y=\cfrac{1}{2}x^2+x} \\\\[-0.35em] ~\dotfill\\\\ \textit{when x = 4, what's "y"?}\qquad y=\cfrac{1}{2}(4)^2+4\implies y=\cfrac{16}{2}+4\implies y=12](/tpl/images/2649/4498/80f05.png)
Find the missing value in the table.
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