a) 4√5 - 8√2 + 21√5 -12√2-7√2+21√5= 46√5-27√2
b) 3√7-6√7+12√3+8√3+20√7= 17√7+20√3
c) -2 x 2√3+2√2+5√3+5 x 2 √2 - 21√3 - 63√2=
= -4√3+5√3-21√3+2√2+10√2-63√2=
= - 20√3 - 51√2
d) 6√5-6√7+( 32√7+ 768√5) : (120√5+ 80√7) : 5=
=6√5-6√7+(4√7+96√5) / (15√5+10√7) x 1/5=
=(6√5-6√7)(75√5+ 50√7) + 4√7+9√5=
=6 x 75 x 5 -6 x 75 x √35 + 50 x 6 x √35 - 6 x 50 x 7 + 4√7+9√5=
=2 250 - 450√35 + 300√35 - 2 100 +4√7+9√5=
=150 - 150√35 +4√7+9√5
