The expression $6y^2-y-51$ can be rewritten as $(3Ay+B)(y-C)$, where $A$, $B$, and $C$ are positive integers. Find $(AC)^2-B$.
That equals (6y + 17)(y - 3), so then A = 2, B = 17, C = 3, and 6^2-17 = 19.
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