Which polynomial is prime?

Combine like terms in choice D to get 10x² − x + 6. Its discriminant is (−1)² − 4(10)(6) = −239, which is not a nonnegative perfect square, so the quadratic cannot be factored into polynomials with integer coefficients. The other choices factor by grouping, so choice D, 10x² − x + 6, is prime.

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