Question

помогите решить -0,3:х=2/5,
-7у(4,8-у)*(5+у)=0
-у:4,8=2,25

Answer 1

Ответ:

1)

$\frac{ - 0.3}{x} = \frac{2}{5}$

$x = \frac{ - 0.3 \times 5}{2} = - 0.75$

2)

$- 7y(4.8 - y) \times (5 + y) = 0$

$- 7y(24 + 4.8y - 5y - {y}^{2} ) = 0$

$- 168y + 1.4 {y}^{2} + 7 {y}^{3} = 0$

$y(7 {y}^{2} + 1.4y - 168) = 0$

$y = 0$

Или

$7 {y}^{2} + 1.4y - 168 = 0$

${y}^{2} + 0.2 - 24 = 0$

$d = {0.2}^{2} - 4 \times ( - 24) \times 1 = 96.04 = {9.8}^{2}$

$x1 = \frac{ - 0.2 - 9.8}{2} = - 5$

$x2 = \frac{ - 0.2 + 9.8}{2} = 4.8$

3)

$\frac{ - y}{4.8} = 2.25$

$- y = 2.25 \times 4.8$

$y = - 10.8$