Решебник по алгебре и начала математического анализа 10 класс Колягин Задание 19

\[\boxed{\mathbf{19}.}\]

\[1)\ 0,2x - 7 = - 0,3 \cdot (x + 4)\]

\[0,2x - 7 = - 0,3x - 1,2\]

\[0,2x + 0,3x = - 1,2 + 7\]

\[0,5x = 5,8\]

\[x = 11,6.\]

\[2)\ 4x - 2 \cdot (x - 1,5) =\]

\[= 3,5 - 3 \cdot \left( \frac{1}{2} - x \right)\]

\[4x - 2x + 3 = 3,5 - 1,5 + 3x\]

\[2x - 3x = 2 - 3\]

\[- x = - 1\]

\[x = 1.\]

\[3)\ x(x + 2) = x^{2} + 5 \cdot (x - 6)\]

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

\[2x - 5x = - 30\]

\[- 3x = - 30\]

\[x = 10.\]

\[4)\ 3x - 2x(x - 1) = 2 \cdot \left( 7 - x^{2} \right)\]

\[3x - 2x^{2} + 2x = 14 - 2x^{2}\]

\[5x = 14\]

\[x = 2,8.\]