Chapter 7: Problem 49
Rationalize each denominator. See Example 4. $$ \frac{8}{1+\sqrt{10}} $$
Short Answer
Expert verified
The rationalized expression is \( -\frac{8}{9} + \frac{8\sqrt{10}}{9} \).
Step by step solution
01
Identify the Conjugate
To rationalize the denominator, we identify the conjugate of the denominator. The conjugate of \(1 + \sqrt{10}\) is \(1 - \sqrt{10}\).
02
Multiply by the Conjugate
Multiply the numerator and the denominator by the conjugate of the denominator: \[\frac{8}{1 + \sqrt{10}} \times \frac{1 - \sqrt{10}}{1 - \sqrt{10}}\]
03
Simplify the Numerator
The new numerator after multiplication becomes:\[8 \times (1 - \sqrt{10}) = 8 - 8\sqrt{10}\]
04
Simplify the Denominator
The new denominator after multiplication became:\[(1 + \sqrt{10})(1 - \sqrt{10}) = 1^2 - (\sqrt{10})^2 = 1 - 10 = -9\]
05
Write the Rationalized Expression
Combine the results from Step 3 and Step 4 to write the rationalized fraction:\[\frac{8 - 8\sqrt{10}}{-9}\]
06
Simplify the Expression
Separate the expression into two terms:\[\frac{8}{-9} - \frac{8\sqrt{10}}{-9} = -\frac{8}{9} + \frac{8\sqrt{10}}{9}\]
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Conjugate Multiplication
When working to rationalize a denominator, one of the key steps involves multiplying by the conjugate. But what is a conjugate? For any binomial expression in the form of \(a + b\), the conjugate is \(a - b\), and vice versa. By multiplying the numerator and the denominator by this conjugate, we effectively work to eliminate the radical expression from the denominator altogether.
- This process relies on the identity \((a + b)(a - b) = a^2 - b^2\), which is based on the difference of squares.
- In our problem, the expression in the denominator, \(1 + \sqrt{10}\), has the conjugate \(1 - \sqrt{10}\).
Simplifying Radicals
Radicals can make mathematical expressions look complicated, and they often need to be simplified for ease of calculation. Simplifying radicals involves expressing them in a form where no perfect square factors greater than 1 remain under the square root symbol.
- In the context of our problem, we look at the denominator \((1 + \sqrt{10})(1 - \sqrt{10})\), which becomes \(1 - 10\).
- This simplification relies on the difference of squares identity, resulting in a neat and clean expression: \(-9\).
Numerator and Denominator Manipulation
Rationalizing often involves a lot of algebraic manipulation of both the numerator and the denominator. The goal is to achieve an expression that is easier to understand or compute, typically with a rational number in the denominator.
- First, we multiply the numerator and the denominator by the conjugate to deal with the term under the square root. This results in transforming the fractions into simpler components.
- For instance, the numerator \(8(1 - \sqrt{10})\) becomes \(8 - 8\sqrt{10}\), as seen in our step-wise solution.
- The denominator, simplified through conjugate multiplication, results in a straightforward integer \(-9\), as shown in the final fraction: \(\frac{8 - 8\sqrt{10}}{-9}\).