Question

Суравнениями, решите только 1 2 3 7 9,13-15 ,19

Answer 1

1.

Объяснение: все решения и ответы на фото

Answer 2

1)

$( - x - 5)(2x + 4) = 0 \\ - 2 {x}^{2} - 4x - 1x - 20 = 0 \\ - 2 {x}^{2} - 5x - 20 = 0 \\ D = { ( - 5)}^{2} - 4 \times ( - 2) \times ( - 20) = 25 - 160$

Дискриминант отрицательный, поэтому нет корней.

2)

$(6x - 3)( - x + 3) = 0 \\ - 6 {x}^{2} + 18x + 3x - 9 = 0 \\ - 6 {x}^{2} + 21x - 9 = 0 \: \: | \div ( - 3) \\ 2 {x}^{2} - 7x + 3 = 0 \\ 2{x}^{2} - x - 6x + 3 = 0 \\ x(2x - 1) - 3(2x - 1) = 0 \\ (2x - 1)(x - 3) = 0 \\ \\ 2x - 1 = 0 \\ 2x = 1 \\ x = 0.5 \\ \\ x - 3 = 0 \\ x = 3$

3)

$( - x - 4)(3x + 3) = 0 \\ - 3 {x}^{2} - 3x - 12x - 12 = 0 \\ - 3 {x}^{2} - 5x - 12 = 0 \\ D = {( - 5)}^{2} - 4 \times ( - 3) \times ( - 12) = 25 - 144$

Дискриминант отрицательный, поэтому нет корней.

7)

${x}^{2} - 36 = 0 \\ {x}^{2} = 36 \\ \\ x = \sqrt{36} \\ x = 6 \\ \\ x = - \sqrt{36} \\ x = - 6$

9)

${x}^{2} - 49 =0 \\ {x}^{2} = 49 \\ \\ x = \sqrt{49} \\ x = 7 \\ \\ x = - \sqrt{49} \\ x = - 7$

13)

$3 {x}^{2} - 9x = 0\\ 3x(x - 3) = 0 \\ \\ 3x = 0 \\ x = 0 \\ \\ x - 3 = 0 \\ x = 3$

14)

$5 {x}^{2} - 10x = 0 \\ 5x(x - 2) = 0 \\ \\ 5x = 0 \\ x = 0 \\ \\ x - 2 = 0 \\ x = 2$

15)

$7 {x}^{2} - 7x = 0 \\ 7x(x - 1) = 0 \\ \\ 7x = 0 \\ x = 0 \\ \\ x - 1 = 0 \\ x = 1$

19)

$9 {x}^{2} = 54x \\ 9 {x}^{2} - 54x = 0 \\ 9x(x - 6) = 0 \\ \\ 9x = 0 \\ x = 0 \\ \\ x - 6 = 0 \\ x = 6$