Given a table of (x, y) values, find the rule. It's pattern-spotting raised to algebra.
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x: 1, 2, 3, 4 → y: 3, 5, 7, 9. Rule?
y goes up by 2 each step. y = 2x + 1. Check: x=4 → 2(4)+1 = 9. ✓
If y goes up by a constant, it's linear: y = mx + b. If the difference of differences is constant, it's quadratic: y = ax² + bx + c.