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Question
If x2 – 4x = 5, the value of x is ______.
Options
5
– 1
5 or – 1
5 and – 1
Solution
If x2 – 4x = 5, the value of x is 5 or – 1.
Explanation:
Given equation should be written as
x2 – 4x – 5 = 0
`\implies` x2 – 5x + x – 5 = 0
`\implies` x(x – 5) + 1(x – 5) = 0
`\implies` (x – 5)(x + 1) = 0
Either x – 5 = 0 or x + 1 = 0
`\implies` x = 5 or – 1
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