6. √21 - 4 = - х

7. √54 - 3 = - х

8. √30 - = - х

9. √56 + = - х

10. √28 + 3 = - х

11. √36 + 5 = - х

12. √14 - 5 = х

13. √28 - 3 = х

14. √2 - = х

15. √12 + = х

16. √48 + 2 = х

17. √21 + 4 = х

18. √-8 + 6 = х

19. √18 + 7 = х

20. √-8 + 9 = х

21. √-35 + 12 = х

22. √-56 + 15 = х

23. √2 + 3 = х

24. √15 - 2 = х

25. √2 + 3 = - х

26. √6 + 5 = х

6.21-4 х=х^2

x^2+4x-21=0

D=16+84=100>0

x1 = (-4-10) / 2=-14/2=-7

x2 = (-4+10) / 2=6/2=3

7.54-3x=x^2

x^2+3x-54=0

D=9+216=225>0

x1 = (-3-15) / 2=-18/2=-9

x2 = (-3+15) / 2=12/2=6

8.30-x=x^2

x^2+x-30=0

D=1+120=121>0

x1 = (-1-11) / 2=-12/2=-6

x2 = (-1+11) / 2=10/2=5

9.56+x=x^2

x^2-x-56=0

D=1+224=225>0

x1 = (1-15) / 2=-14/2=-7

x2 = (1+15) / 2=16/2=8