$4x^2 + 7x + 3 = 0$
$D = 7^2 - 4 * 4 * 3 = 49 - 48 = 1$
$x = \frac{-7 ± \sqrt{1}}{8}$
$x_1 = \frac{-7 - 1}{8} = \frac{-8}{8} = -1$
$x_2 = \frac{-7 + 1}{8} = \frac{-6}{8} = -\frac{3}{4}$
Ответ:
$x_1 = -1$;
$x_2 = -\frac{3}{4}$.

$x^2 + x - 56 = 0$
$D = 1^2 + 4 * 56 = 1 + 224 = 225$
$x = \frac{-1 ± \sqrt{225}}{2}$
$x_1 = \frac{-1 - 15}{2} = \frac{-16}{2} = -8$
$x_2 = \frac{-1 + 15}{2} = \frac{14}{2} = 7$
Ответ:
$x_1 = -8$;
$x_2 = 7$.

$x^2 - x - 56 = 0$
$D = 1^2 + 4 * 56 = 1 + 224 = 225$
$x = \frac{1 ± \sqrt{225}}{2}$
$x_1 = \frac{1 - 15}{2} = \frac{-14}{2} = -7$
$x_2 = \frac{1 + 15}{2} = \frac{16}{2} = 8$
Ответ:
$x_1 = -7$;
$x_2 = 8$.

$5x^2 - 18x + 16 = 0$
$D = 9^2 - 5 * 16 = 81 - 80 = 1$
$x = \frac{9 ± \sqrt{1}}{5}$
$x_1 = \frac{9 - 1}{5} = \frac{8}{5} = 1,6$
$x_2 = \frac{9 + 1}{5} = \frac{10}{5} = 2$
Ответ:
$x_1 = 1,6$;
$x_2 = 2$.

$8x^2 + x - 75 = 0$
$D = 1^2 + 4 * 8 * 75 = 1 + 2400 = 2401$
$x = \frac{-1 ± \sqrt{2401}}{16}$
$x_1 = \frac{-1 - 49}{16} = \frac{-50}{16} = -\frac{25}{8} = -3\frac{1}{8}$
$x_2 = \frac{-1 + 49}{16} = \frac{48}{16} = 3$
Ответ:
$x_1 = -3\frac{1}{8}$;
$x_2 = 3$.

$3x^2 - 11x - 14 = 0$
$D = 11^2 + 4 * 3 * 14 = 121 + 168 = 289$
$x = \frac{11 ± \sqrt{289}}{6}$
$x_1 = \frac{11 - 17}{6} = \frac{-6}{6} = -1$
$x_2 = \frac{11 + 17}{6} = \frac{28}{6} = 4\frac{2}{3}$
Ответ:
$x_1 = -1$;
$x_2 = 4\frac{2}{3}$.

$3x^2 + 11x - 34 = 0$
$D = 11^2 + 4 * 3 * 34 = 121 + 408 = 529$
$x = \frac{-11 ± \sqrt{529}}{6}$
$x_1 = \frac{-11 - 23}{6} = \frac{-34}{6} = \frac{-17}{3} = -5\frac{-2}{3}$
$x_2 = \frac{-11 + 23}{6} = \frac{12}{6} = 2$
Ответ:
$x_1 = -5\frac{-2}{3}$;
$x_2 = 2$.

$x^2 - x - 1 = 0$
$D = 1^2 + 4 * 1 = 1 + 4 = 5$
$x_{1,2} = \frac{1 ± \sqrt{5}}{2}$