If \(x^{2} - kx + 9 = 0\) has equal roots, find the values of
FURTHER MATHEMATICS
WAEC 2017
If \(x^{2} - kx + 9 = 0\) has equal roots, find the values of k.
- A. 3, 4
- B. \(\pm3\)
- C. \(\pm5\)
- D. \(\pm6\)
Correct Answer: D. \(\pm6\)
Explanation
For equal roots, we have that \(b^{2} = 4ac\), so, given a=1, b = -k and c = 9,
\((-k)^{2} = 4\times1\times9 \implies k^{2} = 36\)
\(k = \sqrt{36} = \pm6\)
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