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The number obtained on rationalising the denominator of `(1)/(sqrt(7) - 2)` isA. `(sqrt(7) + 2)/(3)`B. `(sqrt(2) - 2)/(3)`C. `(sqrt(7) + 2)/(5)`D. `(sqrt(7) + 2)/(45)` |
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Answer» Correct Answer - A `(1)/(sqrt(7) - 2) = (1)/(sqrt(7) - 2) . (sqrt(7) + 2)/(sqrt(7) + 2)` , [multiplying numerator and denominator by `sqrt(7) + 2`] `= (sqrt(7) + 2)/((sqrt(7))^(2) - (sqrt(2))^(2)) = (sqrt(7) +2)/(7-4) = (sqrt(7) +2)/(3)` [using identity `(a-b) (a+b) = a^(2) - b^(2)`] |
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