f (x) = a(x - h)^2 + k, where (h, k) is the vertex of the parabola.
Do you see the h and k in your equation?
-h = -(-2) = 2
We see that k = -4.
Our vertex is (2, -4).
In the given question , we have a function given , which is

And we need to find the value of y when x=5.
So we substitute 5 for x and solve for y, that is

And on rounding to the nearest tenths, we will get

So when x=5, y=0.4
136 °Fahrenheit
=
57.7778 °Celsius
If you rounded it, it would be 58 °Celsius.