Răspuns:

a) √15 b)(√5-1)/2 c)1/√2 d)2/3

Explicație pas cu pas:

a) 15/(√5·√3)=15/√15=(√15·√15)/√15=√15

b) (5-√5)/(2√5)=(√5·√5-√5)/(2√5)=√5·(√5-1)/(2·√5)=(√5-1)/2

c) (3-√3)/(3√2-√6)=(√3·√3-√3)/(√3·√3√2-√3·√2)=√3·(√3-1)/[√3·√2·(√3-1)=1/√2

d) (3·√8+2·√12+√20)/(3·√18+2·√27+√45)=

=(3·√4·√2+2·√4·√3+√4·√5·)/(3·√9·√2+2·√9·√3+√9·√5)=

=(3·2·√2+2·2·√3+2·√5·)/(3·3·√2+2·3·√3+3·√5)=

=2·(3·√2+2·√3+√5·)/[3·(3·√2+2·√3+√5)]=2/3