1)4/(a+b) + 5/(a-b) - 10b/(a²-b²)=(4(a-b)+5(a+b)-10b)/(a²-b²)=
=(4a-4b+5a+5b-10b)/(a²-b²)=(9a-9b)/(a²-b²)=
=9(a-b)/(a+b)(a-b)=9/(a+b) , a≠b,a≠-b
Otvet:9/(a+b)
(a²-b²=(a+b)(a-b))
2)(a²+9)/(a³+27) - 1/(a+3) = (a²+9-a²+3a-9)/(a³+27)=
=(3a)/(a³+27), a≠-3
Otvet: 3a/(a³+27)
(a³+27=a³+3³=(a+3)(a²-3a+9))