how do yo write 4.1*10 -3 in expanded form'?

I'm assuming that you want the answer to 4.1 x 10^-3

10^-1 = 0.1

10^-2 = 0.01

10^-3 = 0.001

4.1 x 10^-3  =  4.1 x 0.001  =  0.0041

123. I think you want that. But anyway that is what you would get if you were to solve it.