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ICSE Class 10 Answered

If the sum of first n terms of AP is 6n-n^2 find its 25th term
Asked by lovemaan5500 | 13 Dec, 2017, 06:13: PM
answered-by-expert Expert Answer
begin mathsize 16px style straight S subscript 1 equals 6 minus 1 equals 5 straight S subscript 2 equals 6 cross times 2 minus 2 squared equals 8 straight t subscript 2 equals straight S subscript 2 minus straight S subscript 1 straight t subscript 2 equals 3 straight a equals straight S subscript 1 equals 5 straight d equals straight t subscript 2 space end subscript minus space straight a straight d equals 3 space minus space 5 space straight d space equals space minus 2 Find space 25 to the power of th space term comma straight t subscript 25 equals straight a plus left parenthesis straight n minus 1 right parenthesis straight d equals 5 plus 24 cross times open parentheses negative 2 close parentheses equals negative 43 space end style
Answered by Sneha shidid | 13 Dec, 2017, 07:00: PM

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ICSE 10 - Maths
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