When in doubt, add zero or multiply by one. (English)

Math. Comput. Educ. 50, No. 2, 106-108 (2016).

From the text: In this note we consider a classroom unit designed to show students that the technique of adding zero or multiplying by one using appropriate expressions can often be the best way of solving a given problem. In particular, such a technique should not be considered a “trick", but another useful tool.