A positive number when decreased by 4 is equal to 21 times the reciprocal of the number. The number is?
- 7
- 8
- 9
- None of these
Explanation
Given equation:
x - 4 = 21(1/x)
Multiply both sides by x:
x² - 4x = 21
Rearrange the equation:
x² - 4x - 21 = 0
Factor the quadratic equation:
(x - 7)(x + 3) = 0
Solve for x:
x = 7 (since x is a positive number)
Related MCQs
- 2x² + 4 = 9x
- 2x² + 9 = 4x
- 2x² + 9 = 4x
- x² + 4 = 9x
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