4.
1) (у+3)/2у+2 – (у+1)/2у-2 +
3/у²-1=(у+3)/2(у+1) – (у+1)/2(у-1) + 3/у²-1=
=(у+3)(у-1)/2(у+1)(у-1) – (у+1)(у+1)/2(у-1) (у+1) + 3*2/2(у²-1)=
=((у+3)(у-1) – (у+1)(у+1) + 6 /2(у2-1)=(у2-у+3у-3-у2-у-у-1+6)/2(у²-1)=
= (-3-1+6)/2(у²-1)=2/2(у²-1)=1/(у²-1)
2) (2b²-b)/(b³-1)
– (b-1)/(b²-b+1) =(2b(b-1)/(b-1)(b²+b+1) – (b-1)/(b²-b+1)=
=2b/(b²+b+1) – (b-1)/(b²-b
+1)
5.(a-5b)/b=8 отсюда
a/b - 5 =8
1) a/b=13;
2) (3а- b)/а=(3– b/a)=3-1/13
=2 и 12/13