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प्रश्न
For a G.P. if S5 = 1023 , r = 4, Find a
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उत्तर
Sn = `("a"("r"^"n" - 1))/("r" - 1)`
∴ S5 = `("a"("r"^5 - 1))/("r" - 1)` = 1023, where r = 4
∴ `("a"(4^5 - 1))/(4 - 1)` = 1023
∴ `("a"(1024 - 1))/3` = 1023
∴ a = 3
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