DREAMERS (1) JUQUUICUTROGRESSIUNE S...
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DREAMERS (1) JUQUUICUTROGRESSIUNE SINGLE CORRECT CHOICE TYPE The nth term of a GP is 128 and the sum of its n terms is 255. If its common ratio is 2 then its first term is - (B) 3 (C) 8 (D) None Deko Pages D-a (A) 1

JEE/Engineering Exams
Maths
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Bo giner for a G.P ( rightarrow ) ( a_{n}=128 Rightarrow a r^{n-1}=128 ) ( a(2)^{n-1}=128 ) ( frac{a_{2}^{n}}{2}=128 ) ( 2^{n} a=256 ) ( 2^{n}=frac{256}{a} ) ( & ) ( delta_{n}=255 ) ( Rightarrow frac{aleft(x^{n}-1right)}{r-1}=255 ) ( Rightarrow frac{aleft(2^{n}-1right)}{2-1}=255 ) ( Rightarrow quad aleft(frac{256}{a}-1right)=255 quad(text { furm } 0 ) ( Rightarrow ) ( 256-a=255 ) ( Rightarrow mid a=1 ) Hence of thin ( (A) ) is consect
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