A rational expression can be written in different forms. Some forms are more useful than others when trying to solve problems about rational expressions. A partial fraction decomposition is a way to write a rational expression as a sum of simpler rational expressions that all have constants or linear expressions for numerators. Each decomposition is formed by factoring the denominator and using the factors of the denominator as the denominators of the partial fractions. One use of partial fractions is finding the area under a curve that is a complicated rational expression. This application of partial fractions is encountered in calculus.