If \frac{2 + \sqrt{3}}{2 - \sqrt{3}} = x + y\sqrt{3}, where x and y are integers, what is … — JAMB UTME

If $\frac{2 + \sqrt{3}}{2 - \sqrt{3}} = x + y\sqrt{3}$ , where $x$ and $y$ are integers, what is the value of $x + y$ ?

Answer: 11

The value of

x + y

is 11.

Multiplying the given fraction by

\frac{2 + \sqrt{3}}{2 + \sqrt{3}}

rationalises the denominator to 1 and simplifies the numerator to

7 + 4\sqrt{3}

. Comparing coefficients yields

x = 7

and

y = 4

, making

x + y = 11

Multiply numerator and denominator by the conjugate of the denominator

\frac{(2 + \sqrt{3})(2 + \sqrt{3})}{(2 - \sqrt{3})(2 + \sqrt{3})}

Rationalising the denominator eliminates the surd from the denominator using the identity (a-b)(a+b) = a^2 - b^2.

Expand both the numerator and the denominator

\frac{4 + 4\sqrt{3} + 3}{4 - 3} = \frac{7 + 4\sqrt{3}}{1} = 7 + 4\sqrt{3}

Simplifying algebraic surd multiplication gives integer and surd terms.

Compare terms with x + y\sqrt{3} and solve for x and y

x = 7, y = 4 \implies x + y = 11

Matching rational components and coefficients of \sqrt{3} yields x and y.

Rationalisation of Binomial Denominators containing Surds

Estimated Time:1m 30s

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