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The equation $4 x^{2} - k x + 9 = 0$ has two equal real roots. The positive value of $k$ is:

Competition practiceAlgebra

A12
B6
C36
D144

Step-by-Step Solution

Equal roots ⇒ discriminant = 0:

k^{2} - 4 (4) (9) = 0

⇒

k^{2} = 144

⇒

k = 12

(positive value).

Answer: A) 12

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