1.

If second third and sixth terms of an A.P. are consecutive terms o aG.P. write the common ratio of the G.P.A. 1B. -1C. 3D. -3

Answer» Correct Answer - C
Let a be the first term and d be the common difference of the A.P.
It is given that
a+d,a+2d,a+5d are in GP
`rArr" "(a+2d)^(2)=(a+d)(a+5d)`
`rArr" "4d^(2)+4ad=6ad+5d^(2)rArrd=-2a`
So, the terms are -a,-3a,-9a which are in G.P. with common ratio 3.


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