The equation y = -4x² + bx has a graph that intersects the line y = 2.25 at EXACTLY ONE POINT. Find b > 0.
A3
B4
C5
D6
Answer & Solution
Correct answer: D. 6
At the intersection, -4x² + bx = 2.25 → 4x² - bx + 2.25 = 0. For exactly one solution, discriminant = 0: b² - 4(4)(2.25) = 0 → b² = 36 → b = 6 (taking positive).
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