For instance , the net rate at which a chemical dissolved in a fluid moves toward or away from some point is proportional to the Laplacian of the chemical concentration at that point ; expressed symbolically , the resulting equation is the diffusion equation .
For instance , the net rate at which a chemical dissolved in a fluid moves toward or away from some point is proportional to the Laplacian of the chemical concentration at that point ; the resulting equation is the diffusion equation .