f(x)= 1/3 (x +8)^2 + 5 what the vertex, line of symmetry
Think of the basic parabola
y = x^2
It has its minimum where x=0 because all other values for x produce a positive number when squared. So, the vertex is on the line x=0, which is the line of symmetry.
In this case, you have (x+8)^2
It has its minimum value where x+8 = 0, or x = -8.
So, x = -8 is the line of symmetry, and the vertex is at (-8,5)