how many terms of the ap 21,18,15.......must be added to get the sum 0
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Answered by
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We know that S = n/2(2a + (n-1)d)
= n/2(2 * 21 + (n - 1) * 3)
= n/2(42 - 3n + 3)
= n/2(45 - 3n)
= 45n/2 - 3n^2/2
3n^2 - 45n = 0
On solving the quadratic equation, we get n = 15 or 0.
So, 15 terms must be added to get the sum 0.
Hope this helps!
= n/2(2 * 21 + (n - 1) * 3)
= n/2(42 - 3n + 3)
= n/2(45 - 3n)
= 45n/2 - 3n^2/2
3n^2 - 45n = 0
On solving the quadratic equation, we get n = 15 or 0.
So, 15 terms must be added to get the sum 0.
Hope this helps!
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38
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