Chapter 0: Problem 95
Rationalize the numerator. $$ \frac{1-\sqrt{5}}{3} $$
Short Answer
Expert verified
The rationalized numerator form is \( \frac{-4}{3(1+\sqrt{5})} \).
Step by step solution
01
Identify the Problem
We need to rationalize the numerator of the expression \( \frac{1-\sqrt{5}}{3} \). This process involves eliminating the radical (\(\sqrt{5}\)) from the numerator.
02
Find the Conjugate
To rationalize, we multiply both the numerator and the denominator by the conjugate of the numerator, which is \(1+\sqrt{5}\). This helps in eliminating the square root from the numerator.
03
Multiply Numerator and Denominator
Multiply the numerator and denominator by \(1+\sqrt{5}\):\[\frac{(1-\sqrt{5})(1+\sqrt{5})}{3(1+\sqrt{5})}\]
04
Simplify the Numerator
Use the formula for the difference of squares, \((a-b)(a+b) = a^2 - b^2\), to simplify the numerator: \(1^2 - (\sqrt{5})^2 = 1 - 5 = -4\).
05
Simplify the Expression
Substitute back into the fraction to get:\[\frac{-4}{3(1+\sqrt{5})}\] This is the rationalized form of the original expression with respect to the numerator.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Conjugate
In mathematics, a **conjugate** is a technique used to eliminate square roots (radicals) from the numerator or denominator of a fraction. Conjugates are paired expressions involving the change of a sign between two terms. For example, the conjugate of the expression \(1 - \sqrt{5}\) is \(1 + \sqrt{5}\).
- By multiplying an expression by its conjugate, we aim to cancel out radicals using a special algebraic product called the difference of squares.
- This simplifies the expression because multiplying by the conjugate results in whole numbers.
Difference of squares
The **difference of squares** is a powerful algebraic identity represented by the formula:\[(a - b)(a + b) = a^2 - b^2\]This identity allows you to simplify products of conjugates. Here's how it works:
- In the given exercise, the conjugate \( (1+\sqrt{5}) \) was used to multiply the numerator \( (1-\sqrt{5})(1+\sqrt{5}) \) which forms a difference of squares scenario.
- Applying the formula, \(a = 1\) and \(b = \sqrt{5}\), results in \(1^2 - (\sqrt{5})^2\).
- Calculate each square to get \(1 - 5\), which simplifies directly to \(-4\).
Simplifying radicals
**Simplifying radicals** is another key concept in algebra that involves removing square roots from expressions when possible. Here are the steps typically involved:
- Identify and multiply by a conjugate to eliminate radicals from the numerator or denominator.
- Calculate using the difference of squares to simplify radical terms.
- Re-write the expression without the radical, ensuring it is simpler and more manageable.