Q.If \(x = \sqrt{7 + 4√3}\), find the value of \(x - \cfrac{1}{x}\). (a) 2 (b) 2√3 (c) 4 (d) 2-√3
Answer: B
\(x = \sqrt{7+4√3}\)

\(= \sqrt{4+3+4√3}\)

\(= \sqrt{2^2 + (√3)^2 + 2 \cdot 2 \cdot √3}\)

\(= \sqrt{(2+√3)^2}\)

\(= 2+√3\)


\[ âˆī \cfrac{1}{x} = \cfrac{1}{(2+√3)} = \cfrac{(2-√3)}{(2+√3)(2-√3)} \] \[ = \cfrac{(2-√3)}{4-3} = 2-√3 \]
\[ âˆī x - \cfrac{1}{x} = (2+√3) - (2-√3) \]
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