Editing Partial differential equation (section)

===Fundamental solution===
{{main|Fundamental solution}}
Inhomogeneous equations{{clarification needed|date=July 2020}} can often be solved (for constant coefficient PDEs, always be solved) by finding the [[fundamental solution]] (the solution for a point source <math>P(D)u=\delta</math>), then taking the [[convolution]] with the boundary conditions to get the solution.

This is analogous in [[signal processing]] to understanding a filter by its [[impulse response]].