Limit: lim x→a f(x) = L
  ⇔ ∀ε>0 ∃δ>0: 0<|x−a|<δ → |f(x)−L|<ε
Continuity: f continuous at a iff lim f(x) = f(a)
Derivative: f'(a) = lim h→0 (f(a+h)−f(a))/h
Cauchy sequence: |aₙ − aₘ| → 0

⚡ Example per formula

✏️ Worked Example

Compute lim x→3 (x² − 9) / (x − 3)

(x² − 9)/(x − 3) = (x + 3)(x − 3)/(x − 3) = x + 3 → at x=3, limit = 6.

✅ Answer: 6