Question

find (a) (fog)(x) and domain of (fog). (b) (gof)(x) and domain of (gof)
f(x)=sqrt(x-2) , g(x)=sqrt(x+5)
So far I got this:
a) (fog)(x)= sqrt(sqrt(x+5)-2) this was correct so far. How would I get the domain? (the answer for the domain is [-1, infinity) how do I get this?)
b) (gof)(x)=sqrt(sqrt(x-2)+5)
Domain: [2,infinity)
I dont know how to find domains if the answers have a square root within a square root. Please help! Thank you!