\begin{aligned} &\text { If } a_1, a_2, \ldots a_n \text { are in A.P. where } a_i>0 \text { for all } i \text {, show that }\\ &\frac{1}{\sqrt{a_1}+\sqrt{a_2}}+\frac{1}{\sqrt{a_2}+\sqrt{a_3}}+\cdots+\frac{1}{\sqrt{a_{n-1}}+\sqrt{a_n}} &=\frac{n-1}{\sqrt{a_1}+\sqrt{a_n}} \end{aligned}