a a+2 a a+2 a(a+5)+(a-5)(a+2)
--------------- - -------------- = ------ + -------------- = -------------------------- =
a²-10a+25 25-a² (a-5)² (a+5)(a-5) (a-5)²(a+5)
a²+5a+a²-3a-10 2a² +2a-10 2(a²+a-10)
= ------------------------- = ------------------------ =--------------------
(a-5)(a²-25) (a-5)(a²-25) (a-5)(a²-25)