$x^2+5x+6$ = 0

D = ${\left(\frac{5}{2}\right)}^2-6$ = $\frac{25}{4}$ $-$ $6$ = $\frac{25}{4}$$-$ $\frac{24}{4}$ = $\frac{1}{4}$

x_1,2 = $-\frac{5}{2}$ ± $\sqrt{\frac{1}{4}}$

x₁ = $-\frac{5}{2}$ - $\frac{1}{2}$ = $-\frac{6}{2}$ = -3

x₂ = $-\frac{5}{2}$ + $\frac{1}{2}$ = $-\frac{4}{2}$ = -2

L = { $-3$; $-2$}

$-15+x^2$ = $2x$ | - ( $2x$)

$-15+x^2-2x$ = 0

sortieren

$x^2-2x-15$ = 0

D = ${\left(-1\right)}^2-\left(-15\right)$ = $1$$+$ $15$ = $16$

x_1,2 = $1$ ± $\sqrt{16}$

x₁ = $1$ - $4$ = -3

x₂ = $1$ + $4$ = 5

L = { $-3$; $5$}