WAEC - Further Mathematics (2017 - No. 4)
If \(x^{2} - kx + 9 = 0\) has equal roots, find the values of k.
3, 4
\(\pm3\)
\(\pm5\)
\(\pm6\)
Explicació
For equal roots, we have that \(b^{2} = 4ac\), so, given a=1, b = -k and c = 9,
\((-k)^{2} = 4\times1\times9 \implies k^{2} = 36\)
\(k = \sqrt{36} = \pm6\)