Definition:Order of Differential Equation/Warning

Warning on Order of Differential Equation

Consider the ordinary differential equation:

$y - y + y' - y = 0$

At first glance it looks as though it is of the $2$nd order.

But after some (fairly obvious) simplification, it is seen that it can be written:

$y' - y = 0$

which is of the $1$st order.

Sources

• 1963: Morris Tenenbaum and Harry Pollard: Ordinary Differential Equations ... (previous) ... (next): Chapter $1$: Basic Concepts: Lesson $3$: The Differential Equation