Here's your rational expression: [tex] \frac{u^2-4}{u^2-2u} [/tex]. The numerator of that expression is the difference of perfect squares, and that factors into (u-2)(u+2). In the denominator, you can pull a u out, leaving u(u-2). When you put those factored expressions into its rational form you have [tex] \frac{(u-2)(u+2)}{u(u-2)} [/tex]. We have a common term there, u-2 that will cancel out in the numerator and the denominator. When you cross those out, what you're left with is [tex] \frac{u+2}{u} ,u \neq 0[/tex]. Hopefully, that is a clear enough explanation.
