Over what intervals are following functions continuous let

Question

Over what intervals are the following functions continuous? Justify your answer using the definition of continuity.

a. h(x) = sin (x²)

b. k(x) = 1 / (√(x² + 7) - 4)

Let f and g be twice differentiable functions such that f'(x) ≤ 0 for all x in the domain of f. If h(x) = f(g(x)) and h'(2) = 4. What (if anything) can you say about f, g, and h at x = 2?