Answer: B
\(x = \sqrt{7+4â3}\)
\[ âī \cfrac{1}{x} = \cfrac{1}{(2+â3)} = \cfrac{(2-â3)}{(2+â3)(2-â3)} \] \[ = \cfrac{(2-â3)}{4-3} = 2-â3 \]
\[ âī x - \cfrac{1}{x} = (2+â3) - (2-â3) \]
\(x = \sqrt{7+4â3}\)
\(= \sqrt{4+3+4â3}\)
\(= \sqrt{2^2 + (â3)^2 + 2 \cdot 2 \cdot â3}\)
\(= \sqrt{(2+â3)^2}\)
\(= 2+â3\)
\[ âī \cfrac{1}{x} = \cfrac{1}{(2+â3)} = \cfrac{(2-â3)}{(2+â3)(2-â3)} \] \[ = \cfrac{(2-â3)}{4-3} = 2-â3 \]
\[ âī x - \cfrac{1}{x} = (2+â3) - (2-â3) \]