Źródło TeX:

d(x)=\left\vert AP\right\vert +\left\vert PQ\right\vert +\left\vert QB\right\vert =\sqrt{x^{2}+a_{1}^{2}}+\left\vert PQ\right\vert +\sqrt{(l-x)^{2}+a_{2}^{2}}