How do I write 0.000409 in expanded notation?

Question

Okay. As you can see we are doing expanded notation in Algebra right now. But he(my math teacher) doesn't want it done the easy way. He wants it done the hard way.

Here's an example on how he wants it done from our notes we took today.
example:
4, 070,000 = 4 x 10^6 + 0 x 10^5 + 7 x 10^4.

I don't know how to write 0.000409 in expanded notation. The way my teacher teaches is horrible. He spends most of the class time explaining the easy stuff. But spends only ten minutes on the hard stuff. So I'm confused as I ever will be.

Answer 1

4x10^-4 + 0x10^-5 + 7x10^-6.

You have to have the 0x10^-5 in there to hold the place between the 4 and the 7.

Answer 2

4 x 10^-4 + 9 x 10^-6