# Neglect higher order derivatives in expression

Say I have an expression of this sort:

Derivative[5][x1][t]+Derivative[3][x2][t]+x1[t]+Derivative[2][x1][t]


and so on...

I would like to ask Mathematica to neglext all expressions having derivatives higher than a given order (say N).

What would be a good solution for that?

• – Michael E2 Feb 23 '19 at 15:22

Derivative[5][x1][t] + Derivative[3][x2][t] + x1[t] +

For understanding /; see the documentation of Condition.