Chapter 8: Problem 195
In the following exercises, add. $$ \frac{8}{t+5}+\frac{6}{t-5} $$
Short Answer
Expert verified
\(\frac{14t - 10}{(t+5)(t-5)}\)
Step by step solution
01
- Identify the Common Denominator
To add two fractions, they must have a common denominator. The denominators of the fractions \(\frac{8}{t+5}\) and \(\frac{6}{t-5}\) are \(t+5\) and \(t-5\), respectively. The common denominator will be the product of these two terms: \((t+5)(t-5)\).
02
- Rewrite Each Fraction with the Common Denominator
Rewrite each fraction so that they both have the common denominator \((t+5)(t-5)\). For the first fraction, multiply both the numerator and the denominator by \(t-5\):\[\frac{8(t-5)}{(t+5)(t-5)}\]For the second fraction, multiply both the numerator and the denominator by \(t+5\):\[\frac{6(t+5)}{(t+5)(t-5)}\]
03
- Add the Fractions
Now that both fractions have the same denominator \((t+5)(t-5)\), add the numerators together while keeping the common denominator:\[\frac{8(t-5) + 6(t+5)}{(t+5)(t-5)}\]
04
- Simplify the Numerator
Expand and simplify the numerator:\[8(t-5) + 6(t+5) = 8t - 40 + 6t + 30 = 14t - 10\]The resulting fraction is:\[\frac{14t - 10}{(t+5)(t-5)}\]
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
common denominator
When adding fractions, it’s important to have a common denominator. The common denominator is the shared multiple of the denominators of the fractions. In this exercise, the fractions are \(\frac{8}{t+5}\) and \(\frac{6}{t-5}\). Their denominators are \((t+5)\) and \((t-5)\), which are different. To find the common denominator, follow these steps:
- 1. List the denominators: \((t+5)\) and \((t-5)\)
- 2. Multiply the denominators together: \((t+5)(t-5)\)
rational expressions
Rational expressions are fractions where the numerator and the denominator are polynomials. In our exercise, \(\frac{8}{t+5}\) and \(\frac{6}{t-5}\) are both rational expressions because both the numerators (8 and 6) and the denominators (\(t+5\) and \(t-5\)) are polynomials. Understanding rational expressions involves recognizing:
- The relationship between the numerator and the denominator
- How to manipulate these polynomials to perform operations such as addition, subtraction, multiplication, and division
- The importance of domain restrictions, i.e., the values that the variable can take to avoid division by zero
fraction addition
Adding fractions involves the following steps: finding a common denominator, rewriting the fractions with that common denominator, adding the numerators, and simplifying the result. Here's how it looks in our exercise:
- 1. Find a common denominator: \((t+5)(t-5)\)
- 2. Rewrite each fraction:
For \(\frac{8}{t+5}\), multiply both the numerator and the denominator by \(t-5\): \(\frac{8(t-5)}{(t+5)(t-5)}\)
For \(\frac{6}{t-5}\), multiply both the numerator and the denominator by \(t+5\): \(\frac{6(t+5)}{(t+5)(t-5)}\) - 3. Add the rewritten fractions: \(\frac{8(t-5) + 6(t+5)}{(t+5)(t-5)}\)
- 4. Combine and simplify the numerators: \(\frac{8t - 40 + 6t + 30}{(t+5)(t-5)} = \frac{14t - 10}{(t+5)(t-5)}\)
simplifying expressions
Simplifying expressions is an essential part of working with rational expressions. Once we reach a fraction where the numerator and denominator have common factors, we can potentially simplify further. In our final step:
- Expand the simplified numerator: \(8t - 40 + 6t + 30 = 14t - 10\)
- Write the expanded numerator over the common denominator: \( \frac{14t - 10}{(t+5)(t-5)}\)