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The sum to infinity of the series `1+(4)/(5)+(7)/(5^(2))+(10)/(5^(3))+ . . . ,` is |
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Answer» (ii) ` therefore S_(infty)=1+4((1)/(5))+7((1)/(5))^(2)+10((1)/(5))^(3)+"...." "upto "infty ".....(iii)"` Multiplying both sides of Eq. (i) by `(1)/(5)`, we get `(1)/(5) S_(infty)=((1)/(5))+4((1)/(5))^(2)+7((1)/(5))^(3)+"...." "upto "infty ".....(iv)"` Subtracting Eq. (iv) from Eq. (iii), we get `(1-(1)/(5)) S_(infty)=1+3[((1)/(5))+((1)/(5))^(2)+((1)/(5))^(3)+"...." "upto "infty "]` `=1+3(((1)/(5))/(1-(1)/(5)))=1+(3)/(4)` `=(4)/(5)S_(infty)=(7)/(4)=` `therefore S_(infty)=(35)/(16)` |
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