# 12.8: Rational Equations Using Proportions

**Basic**/ At Grade Created by: CK-12

**Practice**Rational Equations Using Proportions

Suppose you were traveling on a paddle boat at a constant speed. In 6 minutes, you traveled meters, and in 10 minutes, you traveled meters. Could you find the value of in this scenario? If so, how would you do it? After completing this Concept, you'll be able to solve rational equations using proportions so that you can handle this type of problem.

### Solution of Rational Equations

You are now ready to solve rational equations! There are two main methods you will learn to solve rational equations:

- Cross products
- Lowest common denominators

In this Concept you will learn how to solve using cross products.

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Solving a Rational Proportion
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When two rational expressions are equal, a
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proportion
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is created and can be solved using its cross products.

#### Example A

For example, to solve , cross multiply and the products are equal.

Solve for :

#### Example B

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Solve
.
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Solution:
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Notice that this equation has a degree of two; that is, it is a
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quadratic equation.
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We can solve it using the quadratic formula.

#### Example C

Solve .

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Solution:
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Start by cross multiplying:

Since this equation has a squared term as its highest power, it is a quadratic equation. We can solve this by using the quadratic formula, or by factoring.

1. Since there are no common factors, start by finding the product of the coefficient in front of the squared term and the constant:

2. What factors of -6 add up to 5? That would be -6 and 1, since -6+1=-5.

3. Factor, beginning by breaking up the middle term, , as above:

4. Use the Zero Product Principle:

### Guided Practice

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Solve
.
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Solution:
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### Practice

Sample explanations for some of the practice exercises below are available by viewing the following videos. Note that there is not always a match between the number of the practice exercise in the videos and the number of the practice exercise listed in the following exercise set. However, the practice exercise is the same in both. CK-12 Basic Algebra: Solving Rational Equations (12:57)

Solve the following equations.

**
Mixed Review
**

- Divide: .
- Solve for .
- Find the discriminant of and determine the nature of the roots.
- Simplify .
- Simplify .
- Divide: .
- Simplify .

### Image Attributions

## Description

## Learning Objectives

Here you'll learn how to use proportions to find the solutions to rational equations.