# Nonlinear 1o Order D.E.

1. Aug 22, 2012

### pvgomes07

Hello!!

I am taking a self study diff e course, and I have run into a problem with no one to ask for help.
Here is the problem:

d/dt [ h^3(t) + 3h(t)^2 + 3h(t) ] = q(t)

h(t) is output.
q(t) is input.

is this Nonlinear First Order Differential Equation.
But I could not expand to Taylor Series for linearization... :/

I'm trying to find the transfer function.

Thanks!

2. Aug 22, 2012

### HallsofIvy

It should be basic Calculus that
$$\frac{d}{dx}(h^3+ 3h^2+ 3h)= q(t)$$
$$3h^2\frac{dh}{dt}+ 6h\frac{dh}{dt}+ 3\frac{dh}{dt}= (3h^2+ 6h+ 3)\frac{dh}{dt}= q(t)$$
Now what is the linearization of that?

3. Aug 28, 2012

### Staff: Mentor

Maybe this will help:

h3 + 3 h2 + 3h = (h +1)3 -1

4. Aug 29, 2012

### JJacquelin

Hi !
Why not imtegrate it first ?

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5. Mar 30, 2013

### pvgomes07

Yeah! Thank you very much!
:)