If a1,a2,...an are in H.P then the expre...

If `a_1,a_2,...a_n` are in H.P then the expression `a_1a_2+a_2a_3+....+a_ (n-1)a_n` is equal to

`(n-1)(a_1 -a_n)`

`na_(1)a_(n)`

`(n-1)a_(1)a_(n)`

`n(a_1 -a_(n))`.

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