If the definition field of function f (x) = 1ax2 + 4ax + 3 is r, then the value range of real number a is () A. [0,34)B. (0,34)C. (34,+∞)D. (-∞,0)

If the definition field of function f (x) = 1ax2 + 4ax + 3 is r, then the value range of real number a is () A. [0,34)B. (0,34)C. (34,+∞)D. (-∞,0)

∵ f (x) = 1ax2 + 4ax + 3 is defined as R, ∵ AX2 + 4ax + 3 ≠ 0. If a = 0, the inequality is equivalent to 3 ≠ 0. If a ≠ 0, the inequality is equivalent to the discriminant △ = 16a2-12a < 0, that is, 4a2-3a < 0, and the solution is 0 < a < 34. To sum up, a ∈ [0, 34), so: a