For u ∉ Q̄ with uū algebraic, the span of 1, u, ū, P(u), P(u)‾ carries a 2×3 configuration exactly when deg P is 2 or 3

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For u ∉ Q̄ with uū algebraic, the span of 1, u, ū, P(u), P(u)‾ carries a 2×3 configuration exactly when deg P is 2 or 3 · Prove2Me