Let sn=11.4+14.7+17.10+... to n terms. Then limn→∞sn is equal to
A
13
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B
3
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C
14
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D
∞
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Solution
The correct option is D13 sn=11.4+14.7+17.10+...⇒sn=∑∞n=11(3n−2)(3n+1)=∑∞n=113(13n−2−13n+1) Hence limn→∞sn=limn→∞∞∑n=113(13n−2−13n+1)=limn→∞(13(1−13n+1))=13 Hence, option 'A' is correct.