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ICSE Class 10 Answered

If 8times of the 8th term of an AP is equal to 13 times of the 13th term, show that 21st term of an AP is zero.
Asked by Shreyas | 13 Jul, 2018, 08:01: AM
Expert Answer
According to the question,
8t8 = 13t13 
8(a + 7d) = 13(a + 12d)
8a  +56d = 13a + 156d
13a - 8a + 156d - 56d = 0
5a + 100d = 0
a + 20d = 0
t21 = 0
Answered by Sneha shidid | 13 Jul, 2018, 11:00: AM

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