Question

If a(x) = 3x + 1 and b(x)=sqrt x-4, what is the domain of (b o a)(x)?

Answer 1

Assuming that b(x) = sqrt(x-4), then (b o a)(x) = sqrt [ (3x+1) - 4 ]

3x+1-4, the input to function b(x), MUST be ≥ 0.  Therefore, 3x - 3 ≥ 0, or
3(x-1) ≥ 0, or x ≥ 1   (answer)