Question

Помогите,пожалуйста❤️

Answer 1

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Answer 2

1.
$(a - 4)(a + 9) - 5a(1 - 2a) = {a}^{2} - 4a + 9a - 36 - 5a + 10 {a}^{2} = 11 {a}^{2} - 36$


2.
$\frac{3}{x} + \frac{3}{x + 2} = 4 \\ \frac{3}{x} + \frac{3}{x + 2} - 4 = 0 \\ \frac{3(x + 2)}{x(x + 2)} + \frac{3x}{x(x + 2)} - \frac{4x(x + 2)}{x(x + 2)} = 0 \\ \frac{3x + 6 + 3x - 4x(x + 2)}{x(x + 2)} = 0 \\ \frac{6x + 6 - 4 {x}^{2} - 8x}{x(x + 2)} = 0 \\ \frac{ - 4 {x}^{2} - 2x + 6}{x(x + 2)} = 0 \\ \frac{ 2 {x}^{2} + x - 3 }{x(x + 2)} = 0 \\ 2 {x}^{2} + x - 3 = 0 \\d = {b}^{2} - 4ac = 1 - 4 \times 2 \times ( - 3) = 25 \\ x1 = \frac{ - 1 + 5}{2 \times 2} = \frac{4}{4} = 1 \\ x2 = \frac{ -1 - 5}{2 \times 2} = \frac{ - 6}{4} = - \frac{3}{2}$
ОДЗ: x ≠ 0, x ≠ -2

Оба корня удовл.ОДЗ => являются корнями уравнения.
Ответ: -3/2; 1.


3)
$2x + 3y = 10 \\ x - 2y = - 9 \\ \\ x = - 9 + 2y \\ 2( - 9 + 2y) + 3y = 10 \\ \\ x = - 9 + 2y \\ - 18 + 4y + 3y = 10 \\ \\ x = 2y - 9 \\ 7y = 28 \\ \\ x = 2y - 9 \\ y = 4 \\ \\ y = 4 \\ x = - 1$
Ответ: (-1; 4)