A constructive proof is a proof that directly provides a specific example, or which gives an algorithm for producing an example. Constructive proofs are also called demonstrative proofs.

Courant, R. and Robbins, H. "The Indirect Method of Proof." §2.4.4 in What Is Mathematics?: An Elementary Approach to Ideas and Methods, 2nd ed. Oxford, England: Oxford University Press, pp. 86-87, 1996.

Hoffman, P. The Man Who Loved Only Numbers: The Story of Paul Erdős and the Search for Mathematical Truth. New York: Hyperion, p. 229, 1998.

CITE THIS AS:

Weisstein, Eric W. "Constructive Proof." From MathWorld--A Wolfram Web Resource. http://mathworld.wolfram.com/ConstructiveProof.html