(u^2 - 4) / (u-6)(u-2)
Resriction u ≠ 6 and u ≠ 2 (because the denominator cannot be equal lto zero)
Simplification
u^2 - 4 is a difference of two squares, then you can factor it as the product of (u+2)(u-2). So, you can write the expression as:
(u+2)(u-2) / (u-2)(u-6)
Simplify u -2 (because it appears in the numerator and the denominator)
(u + 2) / (u -6), with u ≠2 and u≠6
