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If a, b, c are in A.P., b, c, d are in G.P. and `1/c ,1/d ,1/e`are in A.P. prove that a, c, e are in G.P.

Answer» As a,b and c are in A.P.
`a-b = b-c`
`a/b - 1 = 1-c/b->(1)`
As, b,c and d are in G.P.
`bd = c^2->(2)`
As, 1/c,1/d,1/e are in A.P.
`1/d-1/e = 1/e-1/d`
`1 - d/c = d/e -1->(3)`
From (2)`1-c/b = d/e-1`
From (1)`a/b-1 = d/e-1`
`ae = bd`
As, `bd = c^2,``ae = c^2`,Thus, a,c and e are in G.P.


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