Answer: 6 terms; common difference 10
\[S_n = \frac{n}{2}(t_1 + t_n)\]\[120 = \frac{n}{2}(-5 + 45) = 20n\]\[n = 6\]\[45 = -5 + (6 - 1)d \Rightarrow d = 10\]The A.P. is −5, 5, 15, 25, 35, 45.
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· 24 Oct 2026
AI-verified · Oct 2026
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