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6 terms of the G.P. 1,-2/3,4/9,..... |
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Answer» ong>Answer: Sn = 261 or 2115/829 Step-by-step explanation: we KNOW that 1, 2/3 , 4/9. now. sñ = a( 1 -rñ ) / 1- R. where s = sum of n terms of gp , a = first term of gp , n= n terms of gp, r = COMMON ratio , now a = 1 common ratio = 2/3. 2/3 ÷1 = 2/3 we need to calculate the n terms of gp Sn = 1( 1- 2/3n ) / 1- 2/3 Sn = 1(1-2/3n) ÷ 3-2/3. Sn = 1(1-2n/3) ÷ 1/3 Sn = 3/1 ×(1-2/3n) . now the n terms =6 times of Sn. we get. putting n 6 = Sn. S6 = 3×(1-{2/3}both having square6 ) =. 3× (1- { 124/ 829} , = 3×( 829-124/829). =. 3( 705 / 829) = 3× 0.87. = 261 answer or 2115 / 829 |
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