If the 3rd and the 9th terms of an AP are 4 and -8 respectively, which term of this AP is zero?

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asked Mar 14, 2018 in Mathematics by paayal (26,720 points) 4 6 46

If the 3rd and the 9th terms of an AP are 4 and -8 respectively, which term of this AP is zero?

1 Answer

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answered Mar 14, 2018 by sanjaydas (61,430 points) 5 7 7
selected Mar 15, 2018 by faiz
 
Best answer

Solution: -8 = a + 8d
4 = a + 2d
Or, -8 – 4 = 6d
Or, -12 = 6d
Or, d = -2
Hence, a = -8 + 16 = 8
0 = 8 + -2(n-1)
Or, 8 = 2(n-1)
Or, n-1 = 4

Or, n = 5

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