Q2 of 47 Page 1

For what value of k will k + 9, 2k – 1 and 2k + 7 are the consecutive terms of an A. P.?

We know that three consecutive terms (Say a1, a2 and a3 ) are in AP. If the differences of successive terms are equal.


 


i.e. a2 - a1 = a3 - a2


 


In this case


 


a1 = k + 9


 


a2 = 2k - 1


 


a3 = 2k + 7


 


For these terms to be in AP


 


2k - 1 - (k + 9) = 2k + 7 - (2k - 1)


 


k - 10 = 8


k = 10 + 8


 


k = 18

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