This is less a question of physics and more one of the mathematical minutes, so please bear with me if this is a really dumb question. I am trying to understand an example equation in the textbook that went from [4(2m)^2] / [(4 * 10^-3m)^2] = 2 * 10^6m. It doesn't bother to explain the stages of the simplification, i.e. how it went from the left side to the right side.

I tried doing [4(2m)^2] / [16(10^-3m)^2] = (4m^2) / [4(10^-6m)] = (1m^2) / (10^-6m) but I'm stuck there. Any help would be greatly appreciated.