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PAGE NO.:DATEA the cum DCthat is Skat is the Sumthe-second-term-lurnilanthind-trt texm0d tha ioth and the nth |
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Answer» We have been given ,Sn = 4n -n^2 Just Think The Given Equation Of The Sum Of " n " Terms Is correct for all the terms in the AP , So If you put n=1 You get Sum of 1 terms which is actually the value of first term a1 .It goes like this , Sn = 4n - n^2 = 4(1) - (1)^2= 4 - 1 = 3 so The First Term Is 3. Sum Of 2 Terms Is ...S2 = 4(2) - (2)^2 = 4 Sum of first 2 Terms means a1 + a2 , Now you know a1 and S2 , so S2 - a1 = a2 = 4-3= 1 Now the common difference , a2- a1 = d = 1-3 = -2. Hence The Basic Method Of Doing That was this . Solving for a10 , an , a3 we get ,a3 = -1 ;a10 = -15;an = 5 - 2n ; |
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