$x^2-8x+17$ = 0

D = ${\left(-4\right)}^2-17$ = $16$ $-$ $17$ = $-1$

Da die Diskriminante D < 0 ist, hat die quadratische Gleichung keine Lösunng.

L ={}

$56+15x+x^2$ = 0

sortieren

$x^2+15x+56$ = 0

D = ${\left(\frac{15}{2}\right)}^2-56$ = $\frac{225}{4}$ $-$ $56$ = $\frac{225}{4}$$-$ $\frac{224}{4}$ = $\frac{1}{4}$

x_1,2 = $-\frac{15}{2}$ ± $\sqrt{\frac{1}{4}}$

x₁ = $-\frac{15}{2}$ - $\frac{1}{2}$ = $-\frac{16}{2}$ = -8

x₂ = $-\frac{15}{2}$ + $\frac{1}{2}$ = $-\frac{14}{2}$ = -7

L = { $-8$; $-7$}