Linearity in Differential Equations

[TranscendArcu]

Homework Statement

Is the following differential equation linear:

yy' + 2 = 0

The Attempt at a Solution

I have the definition of linear as being a_0 (t) y^{(n)} + a_1(t) y^{n-1} + a_2 (t) y^{n-2} ... = 0. Now, presumably y is a function of t. Thus, I could define y = a_0 (t) and let n=1. Thus I would satisfy my definition of linearity in differential equations. Thus, the differential equation is linear.

Is it not so?

 

[HallsofIvy]

No, a_0(t) has to be a known function of t, not y or anything involving y. This equation is non-linear because you have a product of things "involving" the dependent variable y.