ГДЗ по алгебре 7 класс Мерзляк Задание 688

\[\boxed{\text{688\ (688).\ }\text{Еуроки\ -\ ДЗ\ без\ мороки}}\]

\[27x^{3} - 1 - 27x^{3} + 36x = 17\]

\[36x = 18\]

\[x = \frac{1}{2} = 0,5\]

\[Ответ:x = 0,5.\]

\[x^{3} + 64 - x\left( x^{2} - 49 \right) = 15\]

\[x^{3} + 64 - x^{3} + 49x = 15\]

\[49x = - 49\]

\[x = - 1\]

\[Ответ:\ x = - 1.\]

\[x^{3} + 216 - x\left( x^{2} - 18x + 81 \right) =\]

\[= 18x^{2} - 54x\]

\[x^{3} + 216 - x^{3} + 18x^{2} - 81x =\]

\[= 18x^{2} - 54x\]

\[- 27x = - 216\]

\[x = 8\]

\[Ответ:x = 8.\]