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Question

If $x = 2 + \sqrt{3}$, find $x - \frac{1}{x}$.

This question was previously asked in
SSC CGL 2025 Tier 2 Paper 1 Question Paper (19-Jan-2026)
The correct answer is
$2\sqrt{3}$

Calculate $\frac{1}{x}$

Given the value of $x$ is $2 + \sqrt{3}$. To find $\frac{1}{x}$, we calculate the reciprocal:

$ \frac{1}{x} = \frac{1}{2 + \sqrt{3}} $

To simplify this fraction, we multiply the numerator and the denominator by the conjugate of the denominator, which is $2 - \sqrt{3}$:

$ \frac{1}{x} = \frac{1}{2 + \sqrt{3}} \times \frac{2 - \sqrt{3}}{2 - \sqrt{3}} $

Using the difference of squares formula $(a+b)(a-b) = a^2 - b^2$ for the denominator:

$ \frac{1}{x} = \frac{2 - \sqrt{3}}{2^2 - (\sqrt{3})^2} = \frac{2 - \sqrt{3}}{4 - 3} = \frac{2 - \sqrt{3}}{1} $

Therefore, $\frac{1}{x} = 2 - \sqrt{3}$.

Calculate $x - \frac{1}{x}$

Now, substitute the values of $x$ and $\frac{1}{x}$ into the expression $x - \frac{1}{x}$:

$ x - \frac{1}{x} = (2 + \sqrt{3}) - (2 - \sqrt{3}) $

Distribute the negative sign:

$ x - \frac{1}{x} = 2 + \sqrt{3} - 2 + \sqrt{3} $

Combine like terms:

$ x - \frac{1}{x} = (2 - 2) + (\sqrt{3} + \sqrt{3}) $ $ x - \frac{1}{x} = 0 + 2\sqrt{3} $

Thus, the final value is $2\sqrt{3}$.

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