ГДЗ по алгебре 7 класс Макарычев Задание 631

\[\boxed{\text{631\ (631).}\text{\ }\text{Еуроки\ -\ ДЗ\ без\ мороки}}\]

\[\textbf{а)}\ 3x(2x - 1) - 6x(7 + x) = 90\]

\[- 45x = 90\]

\[x = - 2\]

\[Ответ:x = - 2.\]

\[\textbf{б)}\ 1,5x(3 + 2x) =\]

\[= 3x(x + 1) - 30\]

\[4,5x + 3x^{2} = 3x^{2} + 3x - 30\]

\[1,5x = - 30\]

\[x = - 30\ :1,5 = - 300\ :15\]

\[x = - 20\]

\[Ответ:x = - 20.\]

\[\textbf{в)}\ 5x(12x - 7) - 4x(15x - 11) =\]

\[= 30 + 29x\]

\[- 20x = 30\]

\[x = 30\ :( - 20) = - 3\ :2\]

\[x = - 1,5\]

\[Ответ:x = - 1,5.\]

\[\textbf{г)}\ 24x - 6x(13x - 9) =\]

\[= - 13 - 13x(6x - 1)\]

\[24x - 78x^{2} + 54x =\]

\[= - 13 - 78x^{2} + 13x\]

\[65x = - 13\]

\[x = - 13\ :65 = - \frac{13}{65} = - \frac{1}{5}\]

\[x = - 0,2\]

\[Ответ:x = - 0,2.\]