3. Simplify 2 √ (4+2 √ 3)-√ (21-12 √ 3)

4. It is known that [a] represents the integer part of real number A, then {1/√( 16-6√ 7)} is equal to:

5. Given 3√ (x+28)-3√ (x-28)=2, find x.

6. Simplify 3 √ {(√ 5-1)/2}-{(√ 5-1)/2} 2