Let f(x)=√7x and g(x)=x+8, whats the smallest number that is the domain of f^o g?

(f○g)(x)=√(7(x+8))

(f○g)(x)=√(7x+56)

Since there is no real square root of a negative value, the smallest value in the domain would make the radicand equal to zero.  x=-8 is the smallest number in the domain of (f○g)(x)