$x^2 - x = 0$
x(x − 1) = 0
$x_1 = 0 : (x - 1)$
$x_1 = 0$;
$x_2 - 1 = 0 : x$
$x_2 - 1 = 0$
$x_2 = 1$.

$p^2 + 15p = 0$
p(p + 15) = 0
$p_1 = 0 : (p + 15)$
$p_1 = 0$;
$p_2 + 15 = 0 : p$
$p_2 + 15 = 0$
$p_2 = -15$.

$5x^2 - 30x = 0$
5x(x − 6) = 0
$5x_1 = 0 : (x - 6)$
$x_1 = 0 : 5$
$x_1 = 0$;
$x_2 - 6 = 0 : 5x$
$x_2 - 6 = 0$
$x_2 = 6$.

$14x^2 + 18x = 0$
2x(7x + 9) = 0
$2x_1 = 0 : (7x + 9)$
$x_1 = 0 : 2$
$x_1 = 0$;
$7x_2 + 9 = 0 : 2x$
$7x_2 + 9 = 0$
$7x_2 = -9$
$x_2 = -\frac{9}{7}$
$x_2 = -1\frac{2}{7}$.