$x^2+x-72$ = 0

D = ${\left(\frac{1}{2}\right)}^2-\left(-72\right)$ = $\frac{1}{4}$$+$ $72$ = $\frac{1}{4}$$+$ $\frac{288}{4}$ = $\frac{289}{4}$

x_1,2 = $-\frac{1}{2}$ ± $\sqrt{\frac{289}{4}}$

x₁ = $-\frac{1}{2}$ - $\frac{17}{2}$ = $-\frac{18}{2}$ = -9

x₂ = $-\frac{1}{2}$ + $\frac{17}{2}$ = $\frac{16}{2}$ = 8

L = { $-9$; $8$}

$7x-18+x^2$ = 0

sortieren

$x^2+7x-18$ = 0

D = ${\left(\frac{7}{2}\right)}^2-\left(-18\right)$ = $\frac{49}{4}$$+$ $18$ = $\frac{49}{4}$$+$ $\frac{72}{4}$ = $\frac{121}{4}$

x_1,2 = $-\frac{7}{2}$ ± $\sqrt{\frac{121}{4}}$

x₁ = $-\frac{7}{2}$ - $\frac{11}{2}$ = $-\frac{18}{2}$ = -9

x₂ = $-\frac{7}{2}$ + $\frac{11}{2}$ = $\frac{4}{2}$ = 2

L = { $-9$; $2$}