Differential Equations
In order to explain what a differential equation is, we need to use certain ideas. These ideas are: equation; formula; function; rate of change; interval; derivative; and integral. In the next few paragraphs, we shall introduce these ideas briefly, with some explanation and examples. It is entirely possible for anyone to understand these ideas rather easily, by collecting true statements about them; no one should feel that because these ideas may be new they cannot be understood readily.