Rationalise the denominator: 1/(sqrt(5) - sqrt(3)).

Answer: 5+32\frac{\sqrt{5} + \sqrt{3}}{2}

Step-by-step solution

Step 1: Identify the conjugate

To rationalize a denominator of the form (a−b)(\sqrt{a} - \sqrt{b}), we multiply both the numerator and the denominator by its conjugate. The conjugate of (5−3)(\sqrt{5} - \sqrt{3}) is (5+3)(\sqrt{5} + \sqrt{3}). This is because when we multiply a binomial by its conjugate, we use the identity (a−b)(a+b)=a2−b2(a-b)(a+b) = a^2 - b^2, which eliminates the square roots.

Step 2: Multiply by the conjugate

We multiply the given fraction by a fraction equivalent to 1, which is 5+35+3\frac{\sqrt{5} + \sqrt{3}}{\sqrt{5} + \sqrt{3}}. This operation does not change the value of the original expression but helps in rationalizing the denominator.

Step 3: Simplify the numerator

Multiplying the numerator by 1 simply results in the conjugate itself, which is (5+3)(\sqrt{5} + \sqrt{3}).

Step 4: Simplify the denominator

Using the algebraic identity (a−b)(a+b)=a2−b2(a-b)(a+b) = a^2 - b^2, we can simplify the denominator. Here, a=5a = \sqrt{5} and b=3b = \sqrt{3}. So, (5)2−(3)2=5−3=2(\sqrt{5})^2 - (\sqrt{3})^2 = 5 - 3 = 2. This eliminates the square roots from the denominator.

Step 5: Write the rationalized expression

By combining the simplified numerator and denominator, we get the final rationalized expression. The denominator is now a rational number (2).

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