# Chapter 5: Writing Linear Equations

## Introduction

What if you were given select pieces of information about a line like its y-intercept and its slope, or two of its points? How could you determine the equation of that line? The goal of this chapter is to find linear equations that model real-life situations. Why is this important? Because given the equation of a line, you can find the value of its variable(s). Based on the information available to you, there are various ways to determine the equation that best represents a real-world scenario. This chapter focuses on several methods for writing linear equations, including slope-intercept form, point-slope form, and standard form. It also teaches you how to determine if two lines are parallel or perpendicular, how to write the equation of a line that is parallel or perpendicular to another, and how to find the line of best fit for a data set.

## Chapter Outline

- 5.1. Determining the Equation of a Line
- 5.2. Forms of Linear Equations
- 5.3. Applications Using Linear Models
- 5.4. Comparing Equations of Parallel and Perpendicular Lines
- 5.5. Families of Lines
- 5.6. Fitting Lines to Data
- 5.7. Linear Interpolation and Extrapolation

### Chapter Summary

## Summary

This chapter begins by thoroughly covering the various ways to write a linear equation given bits and pieces about the line. The methods covered include slope-intercept form, point-slope form, and standard form. Real-world situations that can be modeled and solved by linear equations in these various forms are highlighted as well. The chapter then moves on to parallel and perpendicular lines, with a focus on using slopes to write the equations of lines that are parallel or perpendicular to another line. It wraps up with scatter plots of data, finding the line of best fit for a data set, and making predictions by using equations.