Step 1: Check Continuity For f(x) = {g(x), x < a; h(x), x >= a}: compute lim(x->a-) g(x), lim(x->a+) h(x), and f(a) = h(a). All three must be equal.
Step 2: Check Differentiability Left derivative: lim(h->0-) [f(a+h)-f(a)]/h = g'(a) (usually) Right derivative: lim(h->0+) [f(a+h)-f(a)]/h = h'(a) (usually) Both must be equal for f'(a) to exist.
Step 3: If finding parameters, set up equations:
- Continuity gives one equation
- Equal derivatives gives another equation
Important: Even if g'(x) and h'(x) have limits at a, you should verify using the definition of derivative, not just lim f'(x).