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प्रश्न
Find the sum of the sequence `-1/3, 1, -3, 9, ..........` upto 8 terms.
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उत्तर
Here, `1/(-1/3) = (-3)/1`
= `9/(-3)`
= –3
Thus, the given sequence is a G.P. with first term (a) = `-1/3` and common ratio (r) = –3 ...(∵ r < 1)
Number of terms to be added, n = 8
∴ `S_n = (a(1 - r^n))/(1 - r)`
`=> S_8 = (-1/3(1 - (-3)^8))/(1 + 3)`
= `(-1 + 3^8)/12`
= `1/12 (3^8 - 1)`
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संबंधित प्रश्न
Find the seventh term from the end of the series :
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Show that : x2, b2, y2 are in A.P.
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If a, b, c are in G.P. and a, x, b, y, c are in A.P., prove that `a/x + c/y = 2`
Find the sum of G.P. :
0.3 + 0.03 + 0.003 + 0.0003 + ........... to 8 items.
Find the sum of G.P. :
`(x + y)/(x - y) + 1 + (x - y)/(x + y) + ..........` upto n terms.
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Q 8
The first term of a G.P. is –3 and the square of the second term is equal to its 4th term. Find its 7th term.
