Zaymiey

📐 Mathematics  ·  Principle of Mathematical Induction  ·  JEE

A student proves P(k) implies P(k+1) for every k, but never verifies P(1). Even though the inductive step is logically correct, why does the proof fail?

Answer: Without a verified base case, the chain of implications has no starting point to begin from.

  • A Without a verified base case, the chain of implications has no starting point to begin from
  • B The inductive hypothesis must always be assumed false, not true, for the argument to work
  • C The statement P(n) must instead be proven separately for every even and odd value of n
  • D Strong induction is required instead, since ordinary induction cannot use implications

Correct answer: A. Without a verified base case, the chain of implications has no starting point to begin from

Explanation: Mathematical induction requires both a true base case and a valid inductive step; without an established starting point P(1), the chain of implications P(k) => P(k+1) never gets triggered for any n.

Induction as a Domino ChainP(1): base case fallsP(k) knocks down P(k+1)...and so on, foreverBase case = first domino tipped; inductive step = each domino guaranteed to tip the next one

Mathematical induction works like a row of dominoes: proving the base case P(1) tips the first domino, and proving the inductive step (P(k) ⟹ P(k+1)) guarantees each domino knocks over the next - together these two facts guarantee ALL dominoes fall, without checking each one individually.

Concept context

A proof technique used to establish that a statement is true for every natural number, using a base case and an inductive step.

Read the full Principle of Mathematical Induction notes →