Question

Difficulty: MediumSurds and Rationalization of Denominators

What is the simplified form of the expression 6+2623\frac{\sqrt{6} + \sqrt{2}}{\sqrt{6} - \sqrt{2}} - \sqrt{3}?

  1. 22Answer
  2. B
    2+232 + 2\sqrt{3}
  3. C
    31\sqrt{3} - 1
  4. D
    232\sqrt{3}

Answer

The simplified form of the expression is 22.
Multiplying the numerator and denominator of 6+262\frac{\sqrt{6} + \sqrt{2}}{\sqrt{6} - \sqrt{2}} by the conjugate (6+2)(\sqrt{6} + \sqrt{2}) gives 8+434=2+3\frac{8 + 4\sqrt{3}}{4} = 2 + \sqrt{3}. Subtracting 3\sqrt{3} yields 22.

Step-by-Step Solution

1
Rationalize the denominator of 6+262\frac{\sqrt{6} + \sqrt{2}}{\sqrt{6} - \sqrt{2}}
Multiply numerator and denominator by the conjugate (6+2)(\sqrt{6} + \sqrt{2}) to get (6+2)2(6)2(2)2\frac{(\sqrt{6} + \sqrt{2})^2}{(\sqrt{6})^2 - (\sqrt{2})^2}.
Rationalizing eliminates the surd from the denominator using the difference of two squares identity.
2
Expand the numerator and simplify the fraction
Numerator: (6)2+212+(2)2=6+43+2=8+43(\sqrt{6})^2 + 2\sqrt{12} + (\sqrt{2})^2 = 6 + 4\sqrt{3} + 2 = 8 + 4\sqrt{3}. Denominator: 62=46 - 2 = 4. Fraction simplifies to 8+434=2+3\frac{8 + 4\sqrt{3}}{4} = 2 + \sqrt{3}.
Simplifying radical factors (12=23\sqrt{12} = 2\sqrt{3}) allows division by the common denominator.
3
Subtract 3\sqrt{3} from the rationalized term
(2+3)3=2(2 + \sqrt{3}) - \sqrt{3} = 2.
Subtracting like surd terms cancels out 3\sqrt{3} leaving the rational constant.

Key Concept

Rationalization of Binomial Denominators and Surd Simplification
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