Respuesta :

Remember that
 you must do in this case is composition of both functions: 
 a (x) = 3x + 1 
 b (x) = root (x-4) 
 Making the composition we have: 
 b (a (x)) = root ((3x + 1) -4) 
 Rewriting: 
 b (a (x)) = root (3x-3) 
 b (a (x)) = root (3 (x-1)) 
 Answer: 
 The domain of the function is: x> = 1 
 Equivalently we have [1, inf)