What is the axis of symmetry of h(x) = 5x2 + 40x + 64

The formula for the axis of symmetry (AOS) is -b/2a.
The 'a' and 'b' values can be derived from examining the standard form of the quadratic, 
ax^2+bx+c
In this scenario,
a=5
b=40
Now plug in the values.
-b/2a
-40/2(5)
-40/10
-4
Remember that "-4" is not your answer. Since the AOS is a vertical line of symmetry of any even degree polynomial, your answer would be x = - 4

I hope this helped. Thank you

(6,0) i hope it makes enough sense