Heaviside cover-up method

Summary

The Heaviside cover-up method is a quick way to find coefficients in a partial fraction decomposition. Let $(s - a)^m$ be a factor of the denominator. The coefficient of $1/(s - a)^m$ is found by deleting ("covering up") this factor and evaluating the rest of the fraction at $s = a$. When all roots of the denominator are simple, it gives the whole decomposition, which is why it is a standard step in inverting Laplace transforms.