2+2=4

Nice—2 + 2 = 4.

If you want a quick formal justification (Peano arithmetic) or a short proof you can quote in an exam:

• Define addition recursively: for any a, a + 0 = a and a + S(b) = S(a + b).
• In Peano terms, 2 = S(S(0)) and 4 = S(S(S(S(0)))).
• Compute:
  • 2 + 1 = 2 + S(0) = S(2 + 0) = S(2) = 3
  • 2 + 2 = 2 + S(1) = S(2 + 1) = S(3) = 4

Would you like me to generate practice problems (e.g., more sums, or proofs of properties like commutativity and associativity) or go through another axiom system?