For which value of m does the graph of y = 18x2 + mx + 2 have exactly one x-intercept?

A quadratic has exactly one x-intercept when its discriminant is zero. For 18x² + mx + 2, the discriminant is m² − 4(18)(2), so setting it to zero gives m² = 144 and m = ±12. Of the choices, 12 is listed, so the correct choice is C) 12.

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