Răspuns:
Explicație pas cu pas:
1.
3/√12 = 3/2√3
2/√75 = 2/5√3
3/2√48 = 3/8√3
21/5√27 = 21/15√3 = 7/5√3
3/2√3 - 2/5√3 + 3/8√3 - 7/5√3 = 12/8√3 + 3/8√3 - 9/5√3 = 15/8√3 - 9/5√3
(15/8√3 - 9/5√3) : √6/4 = (15/8√3 - 9/5√3) x 4/√6
=15/2√18 - 36/5√18 = 15/6√2 - 36/15√2 = 5/2√2 - 13/5√2
=25/10√2 - 26/10√2 = -1/10√2 = -√2/20 = B
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2.
6/√45 = 6/3√5 = 2/√5
3/√20 = 3/2√5
1/√80 = 1/4√5
2/√5 - 3/2√5 + 1/4√5 = 8/4√5 - 6/4√5 + 1/4√5 = 3/4√5
3/4√5 : 15/2√10 = 3/4√5 x 2√10/15 = 6√10/60√5 = √2/10 = D
