# Multiplying Rational Expressions: A Comprehensive Tutorial Unlock the secrets of multiplying rational expressions with our step-by-step guide. Learn essential techniques for factoring, simplifying, and handling complex algebraic fractions to boost your math skills.

Now Playing:Multiply rational expressions– Example 0
Intros
1. Review: Multiplying Monomials
Examples
1. Simplifying Rational Expressions Involving Multiplication
State the non-permissible values, then simplify:
$\frac{5x^2y^3}{x^2y^2} \times \frac{9z^3x^4y^2}{15y^3z^2}$
Simplifying rational expressions and restrictions
Notes
$\bullet$ multiplication rule: $x^a \cdot x^b=x^{a+b}$
$\bullet$ division rule: $\frac{x^a}{x^b}=x^{a-b}$
Concept

## Introduction to Multiplying Rational Expressions

Welcome to our lesson on multiplying rational expressions! This fundamental skill in algebra is crucial for solving complex mathematical problems. Before we dive in, I highly recommend watching our introduction video, which provides a visual and step-by-step explanation of the process. Multiplying fractions might seem daunting at first, but it's actually quite similar to multiplying fractions. The key is to multiply the numerators together and the denominators together, then simplify the result. Remember, a rational expression is simply a fraction where the numerator and denominator are polynomials. As we progress, we'll explore techniques for simplifying these expressions and handling common factors. The introduction video will give you a solid foundation, making the rest of our lesson much easier to grasp. So, let's get started on this exciting journey into the world of rational expressions and their multiplication!

Example

Convert Expressions to Factored Form, then multiply
State the non-permissible values, then simplify:
$\frac{5x^2-15x}{30x^2-10x} \times \frac{3x^2+8x-3}{(x^2-9)}$

#### Step 1: Factor the Numerators and Denominators

To simplify the given rational expressions, we first need to factor both the numerators and the denominators. This will make the expressions more readable and easier to work with.

For the numerator $5x^2 - 15x$, both terms are multiples of 5 and x. Therefore, we can factor out $5x$: $5x^2 - 15x = 5x(x - 3)$

For the denominator $30x^2 - 10x$, both terms are multiples of 10 and x. Therefore, we can factor out $10x$: $30x^2 - 10x = 10x(3x - 1)$

Next, we factor the second numerator $3x^2 + 8x - 3$. This is a quadratic expression, and we can use the cross-multiplication method to factor it: $3x^2 + 8x - 3 = (3x - 1)(x + 3)$

Finally, we factor the second denominator $x^2 - 9$. This is a difference of squares: $x^2 - 9 = (x + 3)(x - 3)$

#### Step 2: State the Non-Permissible Values

Non-permissible values are the values of $x$ that make the denominator zero. We need to find these values for each denominator in the expression.

For the first denominator $10x(3x - 1)$: $10x \neq 0 \implies x \neq 0$ $3x - 1 \neq 0 \implies x \neq \frac{1}{3}

For the second denominator$

(x + 3)(x - 3)$:$ x + 3 \neq 0 \implies x \neq -3 x - 3 \neq 0 \implies x \neq 3 $

Therefore, the non-permissible values are$

x \neq 0, \frac{1}{3}, -3, 3$.

#### Step 3: Simplify the Expression

Now that we have factored the expressions and identified the non-permissible values, we can simplify the expression by canceling out common factors in the numerator and the denominator.

The factored form of the expression is:$

\frac{5x(x - 3)}{10x(3x - 1)} \times \frac{(3x - 1)(x + 3)}{(x + 3)(x - 3)} $

We can cancel out the common factors:$

\frac{5x \cancel{(x - 3)}}{10x \cancel{(3x - 1)}} \times \frac{\cancel{(3x - 1)} \cancel{(x + 3)}}{\cancel{(x + 3)} \cancel{(x - 3)}} $

After canceling the common factors, we are left with:$

\frac{5}{10} $

We can further simplify this to:$

\frac{1}{2}

Therefore, the simplified form of the expression is $\frac{1}{2}$.

FAQs

#### 1. What is a rational expression?

A rational expression is an algebraic fraction where both the numerator and denominator are polynomials. For example, (x^2 + 3x) / (x - 2) is a rational expression.

#### 2. How do you multiply rational expressions?

To multiply rational expressions, follow these steps: 1. Factor the numerators and denominators of each expression. 2. Multiply the numerators together and the denominators together. 3. Cancel out any common factors between the new numerator and denominator. 4. Simplify the resulting expression if possible.

#### 3. Why is it important to factor before multiplying rational expressions?

Factoring before multiplication is crucial because it allows you to identify and cancel out common factors more easily. This simplification can significantly reduce the complexity of the final expression and help avoid errors in calculations.

#### 4. What are non-permissible values in rational expressions?

Non-permissible values are those that make the denominator of a rational expression equal to zero, causing the expression to be undefined. It's important to identify these values to determine the domain of the rational function and avoid mathematical errors.

#### 5. How can I improve my skills in multiplying rational expressions?

To improve your skills: 1. Practice regularly with a variety of problems. 2. Focus on factoring techniques and identifying common factors. 3. Double-check your work by multiplying the simplified expression back out. 4. Study common mistakes and learn strategies to avoid them. 5. Use online resources and tutorials for additional practice and explanations.

Prerequisites

Understanding the fundamentals is crucial when tackling complex mathematical concepts like multiplying rational expressions. A solid grasp of prerequisite topics not only makes learning easier but also enhances your problem-solving skills. Let's explore how these foundational concepts contribute to mastering the multiplication of rational expressions.

At the core of this topic lies the ability to multiply fractions and whole numbers. This skill is essential as rational expressions often involve fractional components. Building on this, simplifying rational expressions and understanding restrictions is paramount. This process helps in reducing complex fractions to their simplest form, making multiplication more manageable.

Proficiency in solving polynomials and identifying common factors of polynomials plays a significant role. These skills allow you to break down complex rational expressions into simpler components, facilitating easier multiplication. Additionally, dividing integers and multiplying and dividing monomials are fundamental operations you'll frequently encounter.

Understanding the domain and range of a function is crucial when working with rational expressions. This knowledge helps in identifying non-permissible values, which is essential for avoiding undefined results in your calculations.

Mastery of exponent rules, particularly the negative exponent rule and the power of a product rule, is indispensable. These rules come into play when simplifying and multiplying complex rational expressions, especially those involving variables with exponents.

By solidifying your understanding of these prerequisite topics, you'll be well-equipped to tackle the intricacies of multiplying rational expressions. Each concept builds upon the others, creating a strong foundation for advanced algebraic operations. Remember, mathematics is a cumulative subject, and investing time in mastering these fundamentals will pay dividends as you progress to more complex topics.