Which polynomial is prime?

Combine like terms in choice C: 10x² − 4x + 3x + 6 = 10x² − x + 6. Its discriminant is (−1)² − 4(10)(6) = −239, so it has no rational roots and cannot be factored into linear factors with rational coefficients. The other choices factor by grouping, so choice C, 10x² − x + 6, is prime.

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