The amazing polynomial identity
See also Fibonacci Identity, Lagrange's Four-Square Theorem
References
Conway, J. H. and Guy, R. K. The Book of Numbers. New York: Springer-Verlag, p. 232, 1996.
Petkovsek, M.; Wilf, H. S.; and Zeilberger, D. A=B. Wellesley, MA: A. K. Peters, p. 8, 1996.