The first denominator is x? -2x=(x-2)x

The second denominator is x? -4x+4=(x-2)？

The common factor is x-2.

So:

The denominator of the first fraction is multiplied by (x-2) at the same time, and the numerator uses the square difference formula.

The denominator of the second fraction is multiplied by x at the same time, and the denominator is the square formula of the difference.