What is the line of symmetry of y=1/3(x-5)^2-4

thanks :D
Do I need to make it into the general form to get -b/2a?

No, you can read it right from the vertex equation if you realize that since x is the squared term, the line of symmetry will be a vertical line through the vertex. If y had been the squared term, the line of symmetry would be horizontal.

The vertex is (5, -4). The vertical line through (5, -4) is x = 5. Therefore, the line of symmetry is x = 5

yes you must calculate -b/2a
y=1/3(x-5)^2-4 = x^2/3 - 10/3x +13/3
then -b/2a = (10/3)/(2/3) = 5
line of symmetry => x=5

x = 5

X=5 is the line of symmetry. No need to convert to standard form.