1.

In acertain A.P. the `24 t h`term istwice the `10 t h`term. Provethat the `72 n d`term istwice the `34 t h`term.

Answer» `T24=a+(24-1)d=a+23d`
`T10=a+(10-1)d=a+9d`
`T24=2T10`
`a+23d=2(a+9d)`
`a+23d=2a+18d`
`a=5d`
`T72=a+(72-1)d`
`=a+71d=5d+71d`
`=76d`
`T34=a+(34-1)d`
`=a+33d=5d+33d`
`T34=38d`
`T72=76d`
`T34=38d`
`T72=2T34`


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