If \(x^{2} - kx + 9 = 0\) has equal roots, find the values of k.

  • A 3, 4
  • B \(\pm3\)
  • C \(\pm5\)
  • D \(\pm6\)
waec 2017furthermathematics

The correct answer is D. \(\pm6\)

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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