The trinomial x2 + bx + c factors to (x + m)(x + n). If b is negative and c is positive, what must be true about m and n?

Expanding (x + m)(x + n) gives x² + (m + n)x + mn, so b = m + n and c = mn. Since c is positive, m and n have the same sign; since b is negative, their sum is negative. Therefore both m and n must be negative, which is choice D.

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