Mathematics - Sequence & Series Question with Solution | TestHub

If ${\mathrm{a}}_1,{\mathrm{a}}_2,{\mathrm{a}}_3,\dots {\mathrm{a}}_{4001}$ are terms of an AP such that $\frac{1}{{\mathrm{a}}_1{\mathrm{a}}_2}+\frac{1}{{\mathrm{a}}_2{\mathrm{a}}_3}+\dots .+\frac{1}{{\mathrm{a}}_{4000}{\mathrm{a}}_{4001}}=10$ and ${\mathrm{a}}_2+{\mathrm{a}}_{4000}=50$ then $\left|{\mathrm{a}}_1-{\mathrm{a}}_{4001}\right|$ is equal to