Chapter 4: Problem 31
For Problems 9-50, simplify each rational expression. \(\frac{3 x^{2}-12 x}{x^{3}-64}\)
Short Answer
Expert verified
The simplified expression is \(\frac{3x}{x^2 + 4x + 16}\).
Step by step solution
01
Factor the Numerator
The numerator is \(3x^2 - 12x\). This expression can be factored by taking out the greatest common factor, which is \(3x\). So, \(3x^2 - 12x = 3x(x - 4)\).
02
Factor the Denominator
The denominator is \(x^3 - 64\). This is a difference of cubes, which can be factored using the formula \(a^3 - b^3 = (a-b)(a^2 + ab + b^2)\). Here, \(x^3 - 4^3\) is factored as \((x - 4)(x^2 + 4x + 16)\).
03
Simplify the Expression
Now that both the numerator and the denominator are factored, the expression is \(\frac{3x(x-4)}{(x-4)(x^2 + 4x + 16)}\). The \(x-4\) term is common in both the numerator and the denominator, allowing us to cancel it out.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Factoring Polynomials
Factoring polynomials involves breaking down a complex expression into simpler, multiplicable parts or factors. This is like finding the building blocks of the polynomial. When you factor a polynomial, you're identifying expressions that, when multiplied together, will give back the original polynomial expression. Factoring is essentially about reversing the distributive property. For example, if you have a polynomial like \(3x^2 - 12x\), you start by looking for common factors in each term. In this case, both terms share a common factor of \(3x\), allowing you to express the polynomial as \(3x(x - 4)\). This makes the polynomial simpler and easier to work with, especially when dealing with rational expressions.Polynomials can often be broken down using different methods:
- The Greatest Common Factor (GCF)
- Factoring by grouping
- Using special formulas, like the difference of squares
- Recognizing and applying the difference or sum of cubes
Greatest Common Factor
The greatest common factor (GCF) is the largest factor that divides each term of a polynomial without leaving a remainder. Identifying the GCF is often the first step in the factoring process. It simplifies calculations by reducing the polynomial to its simplest form without altering its value.In the expression \(3x^2 - 12x\), both terms share factors of 3 and \(x\). Here, the GCF is \(3x\), because it is the highest degree of each common factor. Finding the GCF involves:
- Looking at each term of the expression
- Identifying the numerical coefficients and the smallest power of any common variable
- Factoring these from each term to rewrite the expression in a more manageable form
Difference of Cubes
A difference of cubes occurs when you have an expression of the form \(a^3 - b^3\). This structure can be factored using a specific formula, making it a useful technique in simplifying rational expressions.The factoring formula for a difference of cubes is: \[a^3 - b^3 = (a - b)(a^2 + ab + b^2)\]Understanding the formula is key:
- \(a\) and \(b\) represent the cube roots of each respective term.
- The expression \(a - b\) is one factor, capturing the subtraction aspect.
- The other factor, \(a^2 + ab + b^2\), is a trinomial that stems from the property of cubes.