1) a) (x²-20)/(x√5-10)=[(x-2√5)(x+2√5)]/[√5(x-2√5)]=(x+2√5)/√5=(x·√5+10)/5
б) [3a-2√(6ab)+2b]/[√(27a³)-√(8b³)]=
=[√(3a)-√(2b)]²/{[√(3a)-√(2b)]·[3a+√(6ab)+2b]}=[√(3a)-√(2b)]/{·[3a+√(6ab)+2b]}
2) a) 5/√(5-b)=5√(5-b)/(5-b)
б) (3+√a)/(√3-a)=(3+√a)²/(3-a²)
3)
[(5√a/√b)+1/√a]·[2√(ab)/(25a²-b)]=[(5a+√b)/√(ab)]·[2√(ab)/{(5a-√b)·(5a+√b)}]=
=2/(5a-√b)