Chapter 6: Problem 108
Let \(P\), \(Q\), and \(R\) be rational expressions defined as follows. $$P=\frac{6}{x+3}, \quad Q=\frac{5}{x+1}, \quad R=\frac{4 x}{x^{2}+4 x+3}$$ Simplify the complex fraction \(\frac{P+Q}{R}\)
Short Answer
Expert verified
\( \frac{11}{4} + \frac{21}{4x} \)
Step by step solution
01
- Identify the expressions
Given rational expressions are:\[P=\frac{6}{x+3}, \ Q=\frac{5}{x+1}, \ R=\frac{4 x}{x^{2}+4 x+3}\]
02
- Simplify the denominator of R
Factor the denominator of expression R:\[x^{2}+4 x+3 = (x+3)(x+1)\] Thus, \[ R = \frac{4x}{(x+3)(x+1)}\]
03
- Write expression for \ \( \frac{P+Q}{R} \)
Now substitute the simplified values:\[ \frac{P+Q}{R} = \frac{\frac{6}{x+3} + \frac{5}{x+1}}{\frac{4x}{(x+3)(x+1)}} \]
04
- Find common denominator for P and Q
The common denominator for \(P\) and \(Q\) is \((x+3)(x+1)\):\[ \frac{6}{x+3} = \frac{6(x+1)}{(x+3)(x+1)} \] \[ \frac{5}{x+1} = \frac{5(x+3)}{(x+3)(x+1)} \] Therefore,\[ P + Q = \frac{6(x+1) + 5(x+3)}{(x+3)(x+1)} = \frac{6x+6 + 5x + 15}{(x+3)(x+1)} = \frac{11x+21}{(x+3)(x+1)} \]
05
- Simplify the fraction
Since both the numerator \(P + Q\) and the denominator \(R\) have the same denominator \((x+3)(x+1)\), the complex fraction simplifies as follows: \[ \frac{P+Q}{R} = \frac{\frac{11x+21}{(x+3)(x+1)}}{\frac{4x}{(x+3)(x+1)}} = \frac{11x+21}{4x} \]
06
- Simplify the result
Simplify the resulting fraction: \[ \frac{11x+21}{4x} = \frac{11x}{4x} + \frac{21}{4x} = \frac{11}{4} + \frac{21}{4x} \]
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Rational Expressions
A rational expression is a fraction where both the numerator and the denominator are polynomials. For example, in the exercise, the expressions given were:
- P = \(\frac{6}{x+3}\)
- Q = \(\frac{5}{x+1}\)
- R = \(\frac{4 x}{x^{2}+4 x+3}\)
Factoring Polynomials
Factoring polynomials involves expressing a polynomial as a product of its linear factors. It helps in simplifying complex fractions. For instance, part of the solution requires simplifying the expression R. Given:
- \(R = \frac{4 x}{x^{2}+4 x+3}\)
- \(x^{2}+4 x+3 = (x+3)(x+1)\)
- \(R = \frac{4 x}{(x+3)(x+1)}\)
Common Denominators
Finding common denominators is essential when you add or subtract rational expressions. In our case, we needed to find a common denominator for P and Q before summing them. Given:
- \(\frac{6}{x+3}\) and \(\frac{5}{x+1}\)
- \(\frac{6}{x+3} = \frac{6(x+1)}{(x+3)(x+1)}\)
- \(\frac{5}{x+1} = \frac{5(x+3)}{(x+3)(x+1)}\)
- \(\frac{6(x+1) + 5(x+3)}{(x+3)(x+1)} = \frac{11x+21}{(x+3)(x+1)}\)
Simplification
Simplification involves reducing expressions to their simplest form. After obtaining \(\frac{P+Q}{R}\), the goal is to simplify:
- \( \frac{P+Q}{R} = \frac{\frac{11x+21}{(x+3)(x+1)}}{\frac{4x}{(x+3)(x+1)}}\)
- Since both the numerator and the denominator share the same denominator \((x+3)(x+1)\), it simplifies to \(\frac{11x+21}{4x}\).
- \(\frac{11x+21}{4x} = \frac{11x}{4x} + \frac{21}{4x}= \frac{11}{4}+\frac{21}{4x}\)