The sum of an infinite G.P. is 57 and the sum of their cubes is `9457 ,` find the G.P.

Explanation

Let the G.P. is ,

`a,ar,ar^2,...oo`

Then, `a/(1-r) = 57`

` a = 57(1-r)->(1)`

Now, if we take cubes of the terms, then G.P. will be,

`a^3,a^3r^3,a^3r^6,...oo`

Now, sum of the cubes of this G.P.. will be,

`a^3/(1-r^3) = 9457`

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