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Question
If 4 is a root of equation x2 + kx – 4 = 0; the value of k is ______.
Options
3
–3
2
–2
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Solution
If 4 is a root of equation x2 + kx – 4 = 0; the value of k is –3.
Explanation:
Given 4 is a root of equation
x2 + kx – 4 = 0 ...(1)
∴ 4 satisfies given equation (1)
∴ 42 + k × 4 – 4 = 0
`\implies` 16 + 4k – 4 = 0
`\implies` 12 + 4k = 0
`\implies` 4k = – 12
`\implies` k = – 3
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