Chapter 6: Problem 54
Multiply or divide. Write each answer in lowest terms. $$ \frac{(x+4)^{3}(x-3)}{x^{2}-9} \div \frac{x^{2}+8 x+16}{x^{2}+6 x+9} $$
Short Answer
Expert verified
(x + 4) (x + 3)
Step by step solution
01
- Factor Denominators
First, factor the quadratic expressions in the denominators. Note that \(x^2 - 9 = (x-3)(x+3)\) and \(x^2 + 6x + 9 = (x + 3)^2\).
02
- Factor Numerators
Next, factor the quadratic expression in the numerator of the second fraction. Recall that \(x^2 + 8x + 16 = (x + 4)^2\).
03
- Rewrite the Expression
Rewrite the original expression using the factored forms: \[\frac{(x+4)^{3}(x-3)}{(x-3)(x+3)} \ \div \ \frac{(x+4)^{2}}{(x+3)^{2}}.\]
04
- Multiply by the Reciprocal
To divide by a fraction, multiply by its reciprocal: \[\frac{(x+4)^{3}(x-3)}{(x-3)(x+3)} \ \cdot \ \frac{(x+3)^{2}}{(x+4)^{2}}.\]
05
- Simplify the Expression
Cancel out any common factors: \[(x+4)^{3},(x+3),(x-3).\] This simplifies to \[(x+4) (x+3)\].
06
- Final Answer
Combine the remaining factors, so the final simplified expression is: \[(x+4) (x+3)\].
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Factoring Quadratics
Factoring quadratics is a crucial skill when working with rational expressions. A quadratic expression is of the form \(ax^2 + bx + c\), where \(a\), \(b\), and \(c\) are constants. To factor it, you should look for two numbers that multiply to \(ac\) and add up to \(b\).
For example:
For example:
- \(x^2 - 9\) factors into \((x-3)(x+3)\). This is because \(-3\) and \(+3\) are roots of the equation \(x^2 - 9 = 0\).
- \(x^2 + 6x + 9\) factors into \((x+3)^2\). This is because \(3\) and \(3\) are roots of the equation \(x^2 + 6x + 9 = 0\).
- \(x^2 + 8x + 16\) factors into \((x+4)^2\). This is because \(4\) and \(4\) are roots of the equation \(x^2 + 8x + 16 = 0\).
Multiplying Fractions
Multiplying fractions is key when simplifying and manipulating rational expressions. The core rule is to multiply the numerators together and the denominators together.
Here's how you do it:
\[ \frac{(x+4)^{3}(x-3)}{(x-3)(x+3)} \cdot \frac{(x+3)^{2}}{(x+4)^{2}} \]
This helps to create common factors which can be cancelled out.
Here's how you do it:
- Multiply the numerators: If you have \( \frac{a}{b} \) and \( \frac{c}{d} \), the product is \(\frac{ac}{bd}\).
- Use the reciprocal: When dividing fractions, you multiply by the reciprocal of the second fraction. In our problem, we convert the division \(\div\) into a multiplication by flipping the second fraction.
\[ \frac{(x+4)^{3}(x-3)}{(x-3)(x+3)} \cdot \frac{(x+3)^{2}}{(x+4)^{2}} \]
This helps to create common factors which can be cancelled out.
Simplifying Expressions
Simplifying expressions is the art of making a complex mathematical expression easier to understand and work with. Here's how:
- Cancel common factors: Look for terms that appear both in the numerator and the denominator. In the given exercise, we have \((x+4)^2\) in the numerator and denominator which we can cancel out. Similarly, we can cancel \((x-3)\) and \((x+3)\).
- Combine like terms: Once the common factors are canceled, multiply the remaining terms. This results in a simpler form of the expression.
- Step 1: Cancel \((x+4)^2\), \(x-3\), and \(x+3\) to simplify to \(x + 4\) and \(x + 3\).
- Step 2: Combine the remaining terms to reach the final answer: \((x + 4)(x + 3)\).