Question

Помогите с алгеброй.

Answer 1

Ответ:

6.75

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Answer 2

$\frac{1}{k - 7} - \frac{9}{k + 7} = \frac{1}{k - 7} \times \frac{9}{k + 7} \\ \frac{k + 7 - 9k + 63}{(k - 7)(k +7)} = \frac{9}{(k - 7)(k + 7)} \\ \frac{70 - 8k}{(k + 7)(k - 7)} - \frac{9}{(k - 7)(k + 7)} = 0 \\ \frac{61 - 8k}{(k +7 )(k - 7)} = 0 \\ 61 - 8k = 0 \\ - 8k = - 61 \\ k = 7 \frac{5}{8}$

Ответ: 7 5/8,да и ещё k≠±7