When x changed by 4, y changed by negative 1. Or when y changed by negative 1, x changed by 4. So we have to have a constant change in y with respect to x of negative 1/4. Let's see if this is true. So
What is a Linear Differential Equation? Suppose that f: X→Y and f (x)=y, a differential equation without nonlinear terms of the unknown function y and its derivatives is