Your question is: [tex]\frac{8u}{u^2-18u+81} -\frac{72}{u^2-18u+81}[/tex] Then, the above formula equate:
[tex]\frac{8u-72}{u^2-18u+81}[/tex] Factor out 8 from the numerator we get: [tex]\frac{u-9}{u^2-18u+81}[/tex] Factorization of the denominator: [tex]\frac{u-9}{(u-9)^2}[/tex] Simplifying the numerator and the denominator by (u-9) we get: [tex]\frac{1}{(u-9)}[/tex]
