1. 0,5x2 = 0 2. x²-9 = 0 3. 2x² + 15 = 0 4. 3x² + 2x = 0 5. 2x²-16=0 6. 5(x² + 2) = 2(x² + 5) 7. (x + 1)²-4=0 8. -1,5x2 = 0 9. x²-4 = 0 10. 2x² + 7 = 0 11. x² + 9x = 0 12. 81x²-64 = 0 13. 2(x² + 4) = 4(x² + 2) 14. (x - 2)² - 8 = 0. 15. 9x² - 1 = 0 16. 3x - 2x² = 0 17. x² = 3x 18. x²+2x-3= 2x + 6 19. 3x² + 7 = 12x+7 20. 3x² - 48 = 0 21. 3x² - 12 = 0 22. 2x² + 6x = 0 23. 1,8x2 = 0 24. x² + 9 = 0 25. 7x² - 14 = 0 26. x²-3x =0 27. x²-81=0 28. 4x² + 36 = 0

1. 0. 5x² = 0
   x² = 0 / 0.5
   x² = 0
   x = 0
2. x² - 9 = 0
   x² = 9
   x = ±√9
   x₁ = 3, x₂ = -3
3. 2x² + 15 = 0
   2x² = -15
   x² = -15 / 2
   x² = -7.5 (нет решения, т.к. квадрат не может быть отрицательным)
4. 3x² + 2x = 0
   x(3x + 2) = 0
   x = 0 или 3x + 2 = 0
   3x = -2
   x = -2/3
   x₁ = 0, x₂ = -2/3
5. 2x² - 16 = 0
   2x² = 16
   x² = 8
   x = ±√8
   x = ±2√2
   x₁ = 2√2, x₂ = -2√2
6. 5(x² + 2) = 2(x² + 5)
   5x² + 10 = 2x² + 10
   5x² - 2x² = 10 - 10
   3x² = 0
   x² = 0
   x = 0
7. (x + 1)² - 4 = 0
   (x + 1)² = 4
   x + 1 = ±√4
   x + 1 = ±2
   x + 1 = 2 или x + 1 = -2
   x = 2 - 1 или x = -2 - 1
   x₁ = 1, x₂ = -3
8. -1.5x² = 0
   x² = 0 / -1.5
   x² = 0
   x = 0
9. x² - 4 = 0
   x² = 4
   x = ±√4
   x₁ = 2, x₂ = -2
10. 2x² + 7 = 0
    2x² = -7
    x² = -7 / 2
    x² = -3.5 (нет решения, т.к. квадрат не может быть отрицательным)
11. x² + 9x = 0
    x(x + 9) = 0
    x = 0 или x + 9 = 0
    x = -9
    x₁ = 0, x₂ = -9
12. 81x² - 64 = 0
    81x² = 64
    x² = 64 / 81
    x = ±√(64/81)
    x = ±8/9
    x₁ = 8/9, x₂ = -8/9
13. 2(x² + 4) = 4(x² + 2)
    2x² + 8 = 4x² + 8
    2x² - 4x² = 8 - 8
    -2x² = 0
    x² = 0
    x = 0
14. (x - 2)² - 8 = 0
    (x - 2)² = 8
    x - 2 = ±√8
    x - 2 = ±2√2
    x = 2 ± 2√2
    x₁ = 2 + 2√2, x₂ = 2 - 2√2
15. 9x² - 1 = 0
    9x² = 1
    x² = 1 / 9
    x = ±√(1/9)
    x = ±1/3
    x₁ = 1/3, x₂ = -1/3
16. 3x - 2x² = 0
    x(3 - 2x) = 0
    x = 0 или 3 - 2x = 0
    -2x = -3
    x = -3 / -2
    x = 3/2
    x₁ = 0, x₂ = 3/2
17. x² = 3x
    x² - 3x = 0
    x(x - 3) = 0
    x = 0 или x - 3 = 0
    x = 3
    x₁ = 0, x₂ = 3
18. x² + 2x - 3 = 2x + 6
    x² + 2x - 2x = 6 + 3
    x² = 9
    x = ±√9
    x₁ = 3, x₂ = -3
19. 3x² + 7 = 12x + 7
    3x² - 12x = 7 - 7
    3x² - 12x = 0
    3x(x - 4) = 0
    3x = 0 или x - 4 = 0
    x = 0 или x = 4
    x₁ = 0, x₂ = 4
20. 3x² - 48 = 0
    3x² = 48
    x² = 48 / 3
    x² = 16
    x = ±√16
    x₁ = 4, x₂ = -4
21. 3x² - 12 = 0
    3x² = 12
    x² = 12 / 3
    x² = 4
    x = ±√4
    x₁ = 2, x₂ = -2
22. 2x² + 6x = 0
    2x(x + 3) = 0
    2x = 0 или x + 3 = 0
    x = 0 или x = -3
    x₁ = 0, x₂ = -3
23. 1. 8x² = 0
    x² = 0 / 1.8
    x² = 0
    x = 0
24. x² + 9 = 0
    x² = -9 (нет решения, т.к. квадрат не может быть отрицательным)
25. 7x² - 14 = 0
    7x² = 14
    x² = 14 / 7
    x² = 2
    x = ±√2
    x₁ = √2, x₂ = -√2
26. x² - 3x = 0
    x(x - 3) = 0
    x = 0 или x - 3 = 0
    x = 3
    x₁ = 0, x₂ = 3
27. x² - 81 = 0
    x² = 81
    x = ±√81
    x₁ = 9, x₂ = -9
28. 4x² + 36 = 0
    4x² = -36
    x² = -36 / 4
    x² = -9 (нет решения, т.к. квадрат не может быть отрицательным)

Ответ: Решения указаны для каждого уравнения.