1. = 7+3-2√21+7+3+2√21=20
2. =6+2+2√12+6+2-2√12=16
3. (3^1/4+27^1/4)²=√3+√27+2*3 (3^1/4-27^1/4)²=√3+√27-2*3
учтено 2(3*27)^1/4=3 (√3+√27)²=3+27+2√3*27=30+2*9=48
(√3+√27+6)(√3+√27-6)=(√3+√27)²-36=48-36=12
4. =(√2+√8-2*16^1/4+8)(√2+√8+2*16^1/4-8)=
= (√2+√8-4+8)(√2+√8+4-8)=(√2+√8+4)(√2+√8-4)=(√2+√8)²-16=
=2+8+2√16-16=10+8-16=2