The discriminant tells us important information about the roots of a quadratic equation. For ax^2 + bx + c = 0, discriminant = b^2 - 4ac. In 4x^2 - 5x + 1 = 0, a = 4, b = -5, and c = 1. Substituting gives (-5)^2 - 4(4)(1) = 9. Therefore, the correct answer is 9.