Question

Задание на фото 8 класс

Answer 1

$x\neq0 \\ \frac{21}{x} - 1 = 2x \\ \frac{21}{x} - 1 - 2x = 0 \\ \frac{ - 2 {x}^{2} - x + 21 }{x} = 0 \\ - 2 {x}^{2} - x + 21 = 0 \\ 2x {}^{2} + x - 21 = 0 \\ a =2 \\ b = 1 \\ c = - 21\\ D = {b}^{2} - 4ac = 1 {}^{2} - 4 \times 2 \times ( - 21) = \\ = 1 + 168 = 169 \\x _{1} = \frac{ - 1 - 13}{2 \times 2} = - \frac{14}{4} = - 3.5 \\ x_{2} = \frac{ - 1 + 13}{2 \times 2} = \frac{12}{4} = 3$