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If x(3-2/x)=3/x, then the value of x^3-(...

If `x(3-2/x)=3/x`, then the value of `x^3-(1)/(x^3)` is equal to:

A

`(62)/(27)`

B

`(52)/(27)`

C

`(61)/(27)`

D

`(8)/(27)`

Text Solution

AI Generated Solution

The correct Answer is:
To solve the equation \( x(3 - \frac{2}{x}) = \frac{3}{x} \) and find the value of \( x^3 - \frac{1}{x^3} \), we can follow these steps: ### Step 1: Simplify the given equation Starting with the equation: \[ x(3 - \frac{2}{x}) = \frac{3}{x} \] Distributing \( x \) on the left side: \[ 3x - 2 = \frac{3}{x} \] ### Step 2: Eliminate the fraction To eliminate the fraction, multiply both sides by \( x \): \[ x(3x - 2) = 3 \] This simplifies to: \[ 3x^2 - 2x = 3 \] ### Step 3: Rearrange the equation Rearranging gives us a standard quadratic equation: \[ 3x^2 - 2x - 3 = 0 \] ### Step 4: Use the quadratic formula We can solve for \( x \) using the quadratic formula: \[ x = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a} \] where \( a = 3, b = -2, c = -3 \): \[ x = \frac{-(-2) \pm \sqrt{(-2)^2 - 4 \cdot 3 \cdot (-3)}}{2 \cdot 3} \] Calculating the discriminant: \[ x = \frac{2 \pm \sqrt{4 + 36}}{6} = \frac{2 \pm \sqrt{40}}{6} = \frac{2 \pm 2\sqrt{10}}{6} = \frac{1 \pm \sqrt{10}}{3} \] ### Step 5: Calculate \( x - \frac{1}{x} \) Let \( y = x - \frac{1}{x} \). We can find \( y \) using: \[ y = \frac{1 + \sqrt{10}}{3} - \frac{3}{1 + \sqrt{10}} \] To simplify \( \frac{3}{1 + \sqrt{10}} \), multiply numerator and denominator by \( 1 - \sqrt{10} \): \[ \frac{3(1 - \sqrt{10})}{(1 + \sqrt{10})(1 - \sqrt{10})} = \frac{3(1 - \sqrt{10})}{1 - 10} = \frac{3(1 - \sqrt{10})}{-9} = -\frac{1 - \sqrt{10}}{3} \] Thus, \[ y = \frac{1 + \sqrt{10}}{3} + \frac{1 - \sqrt{10}}{3} = \frac{2}{3} \] ### Step 6: Calculate \( x^3 - \frac{1}{x^3} \) Using the identity: \[ x^3 - \frac{1}{x^3} = (x - \frac{1}{x})\left((x - \frac{1}{x})^2 + 3\right) \] Substituting \( y = \frac{2}{3} \): \[ x^3 - \frac{1}{x^3} = \frac{2}{3}\left(\left(\frac{2}{3}\right)^2 + 3\right) = \frac{2}{3}\left(\frac{4}{9} + 3\right) = \frac{2}{3}\left(\frac{4}{9} + \frac{27}{9}\right) = \frac{2}{3}\left(\frac{31}{9}\right) = \frac{62}{27} \] ### Final Answer Thus, the value of \( x^3 - \frac{1}{x^3} \) is: \[ \frac{62}{27} \]
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