Re-check: \( S_n = \frac{n}{2}(2a + (n-1)d) = \frac{n}{2}(6 + (n-1)2) = \frac{n}{2}(2n + 4) = n(n + 2) \). Set to 210: \( n^2 + 2n - 210 = 0 \).

Sun, 03 May 2026 03:35:47 +0000

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