A differential equation is an equation that relates some function with its derivatives.
An ordinary differential equation is an equation containing a function of only one independent variable and its derivatives.
Differential equations are used to describe processes in nature involving varying quantities and their rates of change.

Separation of variables

• x’ = 1 + x²
• (x² +1) y’ = 2x y²

Variation of parameters

• y’ – 3y = x exp(4x)
• y’ = -(y/x) + 1

Lineare equation with constant factors

• y” – 5y’ +6y = exp(-2x)