Answer
$f(x) =0.4(x+2)^2+4$
Work Step by Step
Given: $$\begin{aligned}
f(x) &= 0.6(x+2)^2+4 \ ,\ a= 0.6.
\end{aligned}$$ The best eyeball fit to the data can be found by setting the constant $a= 0.4 $. Hence, we have $f(x) =0.4(x+2)^2+4 $ as the best eyeball fit to the data.
