Contrapositive Math Example 1

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Example 1

easy
Form the contrapositive of: 'If n2n^2 is even, then nn is even.'

Solution

  1. 1
    Recall the structure of the conditional: pqp \Rightarrow q where pp: 'n2n^2 is even' and qq: 'nn is even.'
  2. 2
    The contrapositive is ¬q¬p\neg q \Rightarrow \neg p. Form the negations: ¬q\neg q: 'nn is not even' (i.e., nn is odd), and ¬p\neg p: 'n2n^2 is not even' (i.e., n2n^2 is odd).
  3. 3
    Contrapositive: 'If nn is odd, then n2n^2 is odd.' By the logical equivalence pq¬q¬pp \Rightarrow q \equiv \neg q \Rightarrow \neg p, this statement has exactly the same truth value as the original — and it is in fact true (odd times odd is odd).

Answer

If n is odd, then n2 is odd.\text{If } n \text{ is odd, then } n^2 \text{ is odd.}
The contrapositive negates both parts and swaps them. It is always logically equivalent to the original conditional, making it a powerful tool in proofs.

About Contrapositive

The contrapositive of a conditional statement PQP \Rightarrow Q is ¬Q¬P\neg Q \Rightarrow \neg P, formed by negating both parts and reversing their order — it is always logically equivalent to the original.

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