snell's answer to D's Addmath Sequence Malaysia question.

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snell
Snell's answer
333 answers (A Helpful Person)
1st
a = 26, d = -2

Sn = n/2[2(26) + (n-1)(-2)] = 0
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=> n² - 27n = 0
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=> n = 0 (n.a.) or n = 27

ans: n = 27