Chapter 6: Problem 47
In Exercises \(29-64,\) reduce each fraction to simplest form. $$\frac{5 x^{2}-6 x-8}{x^{3}+x^{2}-6 x}$$
Short Answer
Expert verified
The fraction simplifies to \(\frac{5x + 4}{x(x + 3)}\).
Step by step solution
01
Factor the Numerator
The numerator is \(5x^2 - 6x - 8\). To factor this quadratic expression, we look for two numbers that multiply to \(5 \times (-8) = -40\) and add to \(-6\). These numbers are \(4\) and \(-10\).Thus, we rewrite and factor by grouping: \(5x^2 + 4x - 10x - 8\).Group the terms: \((5x^2 + 4x) + (-10x - 8)\).Factor each group: \(x(5x + 4) - 2(5x + 4)\).Thus, the factored numerator is \((x - 2)(5x + 4)\).
02
Factor the Denominator
The denominator is \(x^3 + x^2 - 6x\). Begin by factoring out the greatest common factor, \(x\), which gives \(x(x^2 + x - 6)\).Now, factor the quadratic \(x^2 + x - 6\):Look for two numbers that multiply to \(-6\) and add to \(1\). The numbers are \(3\) and \(-2\).Rewrite and factor by grouping: \(x^2 + 3x - 2x - 6 = (x^2 + 3x) - (2x + 6)\).Factor each group: \(x(x + 3) - 2(x + 3)\).The factored quadratic is \((x - 2)(x + 3)\).Thus, the factored denominator is \(x(x - 2)(x + 3)\).
03
Simplify the Fraction
Now, we have the fraction \(\frac{(x - 2)(5x + 4)}{x(x - 2)(x + 3)}\).Notice that \(x - 2\) is a common factor in both the numerator and the denominator.Cancel the common factor \(x - 2\), leaving:\[\frac{5x + 4}{x(x + 3)}\].
04
Verify and Write the Final Answer
Ensure that the simplification is correct by checking if any factor can be further reduced. Both \(5x + 4\) and \(x(x + 3)\) have no common factors remaining.Therefore, the simplest form of the fraction is \(\frac{5x + 4}{x(x + 3)}\).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Factoring Quadratic Expressions
Factoring quadratic expressions involves rewriting a quadratic equation, usually in the form \(ax^2 + bx + c\), as a product of its linear factors. This step is essential in simplifying fractions where both the numerator and the denominator are polynomial expressions.
To factor a quadratic expression like \(5x^2 - 6x - 8\), we look for two numbers that multiply to the product of the coefficient of \(x^2\) (5) and the constant term (-8), which is -40. These numbers should also add up to the coefficient of \(x\) (-6). In this case, the numbers are 4 and -10.
Once found, these numbers allow us to break down the middle term and use grouping to factor the polynomial:
To factor a quadratic expression like \(5x^2 - 6x - 8\), we look for two numbers that multiply to the product of the coefficient of \(x^2\) (5) and the constant term (-8), which is -40. These numbers should also add up to the coefficient of \(x\) (-6). In this case, the numbers are 4 and -10.
Once found, these numbers allow us to break down the middle term and use grouping to factor the polynomial:
- Rewriting: \(5x^2 - 6x - 8\) becomes \(5x^2 + 4x - 10x - 8\).
- Grouping: \((5x^2 + 4x) + (-10x - 8)\).
- Factoring each group: \(x(5x + 4) - 2(5x + 4)\).
Greatest Common Factor
Before factoring a polynomial, it's often helpful to identify and factor out the Greatest Common Factor (GCF). The GCF is the largest factor that divides each term of the polynomial.
Consider the denominator \(x^3 + x^2 - 6x\) in the given fraction. Here, the GCF is \(x\) because it is common to all terms and can be factored out:
After factoring out the GCF, the remaining quadratic \(x^2 + x - 6\) can be further factored into \((x - 2)(x + 3)\). Identifying the GCF is a crucial initial step in polynomial simplification because it reduces the complexity of the polynomial, allowing for further factorization steps.
Consider the denominator \(x^3 + x^2 - 6x\) in the given fraction. Here, the GCF is \(x\) because it is common to all terms and can be factored out:
- Express the polynomial as: \(x(x^2 + x - 6)\).
After factoring out the GCF, the remaining quadratic \(x^2 + x - 6\) can be further factored into \((x - 2)(x + 3)\). Identifying the GCF is a crucial initial step in polynomial simplification because it reduces the complexity of the polynomial, allowing for further factorization steps.
Polynomial Long Division
Polynomial long division is a method to simplify or divide large polynomial expressions. While not directly used in this task, understanding its principle is important for situations where simplifying a fraction isn't as straightforward.
Imagine you have a complex polynomial that can't be easily factored. Polynomial long division becomes useful here. It is similar to numerical long division, breaking down a polynomial by dividing it by another polynomial, often simplifying a complex expression.
In cases where factorization doesn't yield obvious results, or some terms still appear complicated, polynomial long division is a tool to consider. It systematically reduces one polynomial by another, separating it into a quotient and remainder—a useful technique if simplification stalls by other means.
Imagine you have a complex polynomial that can't be easily factored. Polynomial long division becomes useful here. It is similar to numerical long division, breaking down a polynomial by dividing it by another polynomial, often simplifying a complex expression.
In cases where factorization doesn't yield obvious results, or some terms still appear complicated, polynomial long division is a tool to consider. It systematically reduces one polynomial by another, separating it into a quotient and remainder—a useful technique if simplification stalls by other means.
- Polynomial long division splits the process into repeated steps of dividing, multiplying, and subtracting, mimicking the structure of traditional long division.