$2x^2 - 7x + a = 2(x - 4)(x - x_2)$
$x_1 = 4$
$x_1 + x_2 = -\frac{b}{a} = -\frac{-7}{2} = 3,5$
$4 + x_2 = 3,5$
$x_2 = 3,5 - 4$
$x_2 = -0,5$
$x_1x_2 = \frac{c}{a} = \frac{a}{2}$
$\frac{a}{2} = 4 * (-0,5)$
$\frac{a}{2} = -2$
a = −4
Ответ: при a = −4

$4x^2 - ax + 6 = 4(x - x_1)(x - x_2) = 2 * 2(x - x_1)(x - x_2) = 2 * (2x - 2x_1) * (x - x_2)$
$2x - 2x_1 = 2x + 1$
$-2x_1 = 1$
$x_1 = -0,5$
$x_1x_2 = \frac{c}{a} = \frac{6}{4} = \frac{3}{2} = 1,5$
$-0,5 * x_2 = 1,5$
$x_2 = -\frac{1,5}{0,5}$
$x_2 = -\frac{15}{5}$
$x_2 = -3$
$x_1 + x_2 = -\frac{b}{a} = -\frac{-a}{4} = \frac{a}{4}$
$\frac{a}{4} = -0,5 + (-3)$
$\frac{a}{4} = -3,5$
a = −3,5 * 4
a = −14
Ответ: при a = −14