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If 9 times the 9th term of an A.P. is equal to 13 times the 13th term, then the 22nd term of the A.P. is ______. - Mathematics

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प्रश्न

If 9 times the 9th term of an A.P. is equal to 13 times the 13th term, then the 22nd term of the A.P. is ______.

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उत्तर

If 9 times the 9th term of an A.P. is equal to 13 times the 13th term, then the 22nd term of the A.P. is 0.

Explanation:

Tn = a + (n – 1)d

∴ T9 = a + 8d

And T13 = a + 12d

As per the given condition

9[a + 8d] = 13[a + 12d]

⇒ 9a + 72d = 13a + 156d

⇒ – 4a = 84d

⇒ a = – 21d   .....(i)

Now T22 = a + 21d 

= – 21d + 21d

= 0   ....[From equation (i)]

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अध्याय 9: Sequences and Series - Exercise [पृष्ठ १६३]

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एनसीईआरटी एक्झांप्लर Mathematics [English] Class 11
अध्याय 9 Sequences and Series
Exercise | Q 19 | पृष्ठ १६३

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