For which positive value of k does 4x² + kx + 49 = 0 have two equal real roots?

28. Equal roots need k² − 4 × 4 × 49 = 0 → k² = 784 → k = 28 (taking the positive value).

For which positive value of $k$ does $4 x^{2} + k x + 49 = 0$ have two equal real roots?

Competition practiceAlgebra

Equal roots need

k^{2} - 4 \times 4 \times 49 = 0

→

k^{2} = 784

→

k = 28

(taking the positive value).

Answer: A) 28

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