y = 5x

$y_1 = 5x_1 = 5 * 0 = 0$;
$y_2 = 5x_2 = 5 * 1 = 5$.

y = 0,8x

$y_1 = 0,8x_1 = 0,8 * 0 = 0$;
$y_2 = 0,8x_2 = 0,8 * 5 = 4$.

$y = -\frac{1}{6}x$

$y_1 = -\frac{1}{6}x_1 = -\frac{1}{6} * 0 = 0$;
$y_2 = -\frac{1}{6}x_2 = -\frac{1}{6} * 6 = -1$.