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Let Sn denote the sum of first n terms of an A.P.If S4/S2=4,then Sn+1/Sn is equal to-----------------

Let Sn denote the sum of first n terms of an A.P.If S4/S2=4,then Sn+1/Sn is equal to-----------------


 

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1 Answers

Badiuddin askIITians.ismu Expert
148 Points
13 years ago

Dear sri

let first term is a and common difference is d

 S4 = 2(2a + 3d)

 S2 = 2a +d

 given 2(2a + 3d)/(2a +d) = 4

          2a + 3d = 4a + 2d

             d = 2a ...........1

now Sn+1 /Sn  = (n+1)/2 [2a+ nd] / n/2[2a +(n-1)d]

                      = (n+1)[ 1+n]/n[n]

                      =(1+1/n)2

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