Zgjidh a/r<0.4kL/r5

$$\frac{ a }{ r } < 0.4 \frac{ kL }{ r } 5$$

Gjej r

$$\left\{\begin{matrix}r<0\text{, }&a>2Lk\\r>0\text{, }&a<2Lk\end{matrix}\right.$$

Gjej k

$$\left\{\begin{matrix}k>\frac{a}{2L}\text{, }&\left(L>0\text{ and }r>0\right)\text{ or }\left(L<0\text{ and }r<0\right)\\k\in \mathrm{R}\text{, }&\left(a>0\text{ and }r<0\text{ and }L=0\right)\text{ or }\left(a<0\text{ and }r>0\text{ and }L=0\right)\\k<\frac{a}{2L}\text{, }&\left(r>0\text{ and }L<0\right)\text{ or }\left(L>0\text{ and }r<0\right)\end{matrix}\right.$$