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प्रश्न
Find the first term of the G.P. whose common ratio 5 and whose sum to first 6 terms is 46872
उत्तर
Common ratio, r = 5
S6 = 46872
∴ `("a"("r"^6 - 1))/("r" - 1)` = 46872
⇒ S6 = `("a"(5^6 - 1))/(5 - 1)` = 46872
⇒ a = `(46872 xx 4)/([25 xx 25 xx 25 - 1])`
⇒ a = `187488/15624` = 12
⇒ first term = 12
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