ГДЗ по алгебре 7 класс Макарычев Задание 697

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\[\textbf{а)}\ (3x - 1)(5x + 4) - 15x^{2} = 17\]

\[15x^{2} + 12x - 5x - 4 - 15x^{2} =\]

\[= 17\]

\[7x = 17 + 4\]

\[7x = 21\]

\[x = 3\]

\[Ответ:x = 3.\]

\[\textbf{б)}\ (1 - 2x)(1 - 3x) =\]

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

\[1 - 3x - 2x + 6x^{2} = 6x^{2} - x - 1\]

\[1 - 5x + 6x^{2} - 6x^{2} + x = - 1\]

\[- 4x = - 1 - 1\]

\[- 4x = - 2\]

\[x = 0,5\]

\[Ответ:x = 0,5.\]

\[\textbf{в)}\ 12 - x(x - 3) =\]

\[= (6 - x)(x + 2)\]

\[12 - x^{2} + 3x =\]

\[= 6x + 12 - x^{2} - 2x\]

\[- x = 0\]

\[x = 0\]

\[Ответ:x = 0.\]

\[\textbf{г)}\ (x + 4)(x + 1) =\]

\[= x - (x - 2)(2 - x)\]

\[x^{2} + x + 4x + 4 =\]

\[= x - \left( - x^{2} + 2x - 4 + 2x \right)\]

\[8x = 0\]

\[x = 0\]

\[Ответ:x = 0.\]