The term "autonomous" refers to an ordinary differential equation that relates the derivatives of the dependent variable as a function *only* of the dependent variable. In other words, the ODE doesn't explicitly depend on the independent variable.
Examples:
is autonomous
is *not* autonomous
3s+28=85, take away 28 from both sides of the equals to give you 3s=57, divide by 3 on both side to give you s=19.
They definitely can be positive they can be negative and they can have an absolute value but I would choose they both can be positive and negative