5. Решите уравнение: 1) 3x² + 12x = 0; 2) -4x + 20x2 = 0; 3) 0,5x²+3x = 0; 4) 0,8x²-4x = 0; 5) -2/15x² = 4x; 6) -3/2x = 6x².

1. 3x² + 12x = 0

   3x(x + 4) = 0

   x = 0 или x + 4 = 0

   x = 0 или x = -4

2. -4x + 20x² = 0

   4x(5x - 1) = 0

   x = 0 или 5x - 1 = 0

   x = 0 или 5x = 1

   x = 0 или x = 0,2

3. 0,5x² + 3x = 0

   0,5x(x + 6) = 0

   x = 0 или x + 6 = 0

   x = 0 или x = -6

4. 0,8x² - 4x = 0

   0,8x(x - 5) = 0

   x = 0 или x - 5 = 0

   x = 0 или x = 5

5. $$- \frac{2}{15}x^2 = 4x$$

   $$ - \frac{2}{15}x^2 - 4x = 0$$

   $$x(-\frac{2}{15}x - 4) = 0$$

   x = 0 или $$-\frac{2}{15}x - 4 = 0$$

   $$-\frac{2}{15}x = 4$$

   $$x = 4 \times (-\frac{15}{2})$$

   x = 0 или x = -30

6. $$- \frac{3}{2}x = 6x^2$$

   $$6x^2 + \frac{3}{2}x = 0$$

   $$x(6x + \frac{3}{2}) = 0$$

   x = 0 или $$6x + \frac{3}{2} = 0$$

   $$6x = -\frac{3}{2}$$

   $$x = -\frac{3}{2} \times \frac{1}{6}$$

   x = 0 или x = -$$\frac{1}{4}$$

Ответ: 1) x = 0, x = -4; 2) x = 0, x = 0,2; 3) x = 0, x = -6; 4) x = 0, x = 5; 5) x = 0, x = -30; 6) x = 0, x = -1/4