Chapter 7: Problem 51
Rationalize each denominator. See Example 4. $$ \frac{\sqrt{x}}{\sqrt{x}+\sqrt{y}} $$
Short Answer
Expert verified
\( \frac{x - \sqrt{xy}}{x - y} \)
Step by step solution
01
Identify the Conjugate
The expression given is \( \frac{\sqrt{x}}{\sqrt{x}+\sqrt{y}} \). To rationalize the denominator, we need to multiply both the numerator and denominator by the conjugate of the denominator, which is \( \sqrt{x}-\sqrt{y} \).
02
Multiply by the Conjugate
Multiply the expression by \( \frac{\sqrt{x}-\sqrt{y}}{\sqrt{x}-\sqrt{y}} \):\[\frac{\sqrt{x}}{\sqrt{x}+\sqrt{y}} \cdot \frac{\sqrt{x}-\sqrt{y}}{\sqrt{x}-\sqrt{y}}\]
03
Simplify the Denominator
The denominator becomes a difference of squares:\[(\sqrt{x} +\sqrt{y})(\sqrt{x} - \sqrt{y}) = x - y\]
04
Simplify the Numerator
The numerator is expanded as follows:\[\sqrt{x}(\sqrt{x} - \sqrt{y}) = x - \sqrt{xy}\]
05
Write the Rationalized Expression
Combine the simplified numerator and denominator:\[\frac{x - \sqrt{xy}}{x - y}\]
06
Confirm Simplification
The expression \( \frac{x - \sqrt{xy}}{x - y} \) is now fully simplified with a rationalized denominator.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Conjugate Pairs
When dealing with irrational denominators, like those containing square roots, a common strategy to simplify them is utilizing the conjugate pair. The conjugate of an expression \(a + b\) is \(a - b\), and vice-versa. This technique is specifically useful because it leverages the difference of squares identity, which eliminates the square roots in the denominator.
- For example, the conjugate of \(\sqrt{x} + \sqrt{y}\) is \(\sqrt{x} - \sqrt{y}\).
- Multiplying by this conjugate will help us remove the square roots from the denominators.
Difference of Squares
The difference of squares is a fundamental algebraic identity often used when rationalizing denominators with conjugate pairs. The identity can be written as:\[ (a+b)(a-b) = a^2 - b^2 \]
- In the case of \(\sqrt{x} + \sqrt{y}\) and \(\sqrt{x} - \sqrt{y}\), applying the difference of squares results in \(x - y\), a simplified integer or rational number.
- This mechanism nullifies the square roots, effectively transforming them into whole numbers.
Simplifying Expressions
Simplifying expressions is a crucial part of working with algebraic fractions and involves reducing expressions to their simplest form while preserving their worth.
- Upon rationalizing a denominator using conjugate pairs and the difference of squares, it's essential to simplify the entire expression for the most clarified result.
- After applying the conjugate, the expression in the example: \(\frac{\sqrt{x}}{\sqrt{x}+\sqrt{y}}\) becomes \(\frac{x - \sqrt{xy}}{x-y}\).