$x^2+11x+28$ = 0

D = ${\left(\frac{11}{2}\right)}^2-28$ = $\frac{121}{4}$ $-$ $28$ = $\frac{121}{4}$$-$ $\frac{112}{4}$ = $\frac{9}{4}$

x_1,2 = $-\frac{11}{2}$ ± $\sqrt{\frac{9}{4}}$

x₁ = $-\frac{11}{2}$ - $\frac{3}{2}$ = $-\frac{14}{2}$ = -7

x₂ = $-\frac{11}{2}$ + $\frac{3}{2}$ = $-\frac{8}{2}$ = -4

L = { $-7$; $-4$}

$54+x^2+15x$ = 0

sortieren

$x^2+15x+54$ = 0

D = ${\left(\frac{15}{2}\right)}^2-54$ = $\frac{225}{4}$ $-$ $54$ = $\frac{225}{4}$$-$ $\frac{216}{4}$ = $\frac{9}{4}$

x_1,2 = $-\frac{15}{2}$ ± $\sqrt{\frac{9}{4}}$

x₁ = $-\frac{15}{2}$ - $\frac{3}{2}$ = $-\frac{18}{2}$ = -9

x₂ = $-\frac{15}{2}$ + $\frac{3}{2}$ = $-\frac{12}{2}$ = -6

L = { $-9$; $-6$}