1.

निम्नलिखित श्रेणियों के अनन्त पदों का योग ज्ञात कीजिए | `1+2.(1)/(3)+3.(1)/(3^(2))+4.(1)/(3^(3))`+…

Answer» Correct Answer - `(9)/(4)`
(a)दी गई श्रेणी को इस प्रकार लिख सकते हैं,
`1.1+2((1)/(3))+3((1)/(3))^(2)+4((1)/(3))^(3)+`...
`S_(oo)=1.1+2((1)/(3))+3((1)/(3))^(2)+4((1)/(3))^(3)+....`
`rArr " "(1)/(3)S_(oo)=1.(1)/(3)+2((1)/(3))^(2)+3((1)/(3))^(3)+4((1)/(3))^(4)+...oo`
`rArr " "S_(oo)-(1)/(3)S_(oo)=1+(1)/(3)+(1)/(3^(2))+(1)/(3^(3))+(1)/(3^(4))+...+oo`
`rArr ""(2)/(3)S_(oo)=(1)/(1-(1)/(3))=(3)/(2) rArr S_(oo)=(9)/(4)`


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