So n ≈ ( -7 + 51.85 ) / 6 ≈ 7.475
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- However, in high school level, expect integer.
- Actually, double-check discriminant: 7² + 4×3×220 = 49 + 2640 = 2689, √2689 = ?
- 51² = 2601, 52² = 2704 → 2689 - 2601 = 88 → √2689 ≈ 51.85
- So no integer n.
- But if question is correct, answer is not integer — not suitable.
- Therefore, correct the problem: suppose Sₙ = 98 → n = 7
