Find the domain of f(x)= 3/((square root)x-7(end square root)) Write in interval notation. How would that be done?

Also what would be the domains of:

(x^2)-13*x+x+8

(x^2)-13*x-(x+8)

[(x^2)-13*x]*(x+8)

and also the domain of f+g

f-g

fg

given that f(x)=(square root)8+x(end square root) and g(x)=(square root)8-x(end square root)