If the solution set of \(x^{2} + kx - 5 = 0\) is (-1, 5), find the value of k.
Take Free Practice Test On 2026 JAMB UTME, Post UTME, WAEC SSCE, GCE, NECO SSCE
Correct Answer: Option B
Explanation:
Given x = (-1, 5) for the equation \(x^{2} + kx - 5 = 0\)
\(x = -1 \implies x + 1 = 0\); \(x = 5 \implies x - 5 = 0\)
\((x + 1)(x - 5) = 0\), expanding,
\(x^{2} - 5x + x - 5 = 0 \therefore x^{2} - 4x - 5 = 0\)
\(\therefore\) k = -4.
Given x = (-1, 5) for the equation \(x^{2} + kx - 5 = 0\)
\(x = -1 \implies x + 1 = 0\); \(x = 5 \implies x - 5 = 0\)
\((x + 1)(x - 5) = 0\), expanding,
\(x^{2} - 5x + x - 5 = 0 \therefore x^{2} - 4x - 5 = 0\)
\(\therefore\) k = -4.