Question

If x² – 4x = 5, the value of x is ______.

Options

• 5

• – 1

• 5 or – 1

• 5 and – 1

Answer 1

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