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Introduction and Summary

The last chapter explained how to draw graphs from equations. This chapter explains how to write equations from graphs of lines.

There are several different forms of a linear equation can take. Slope-intercept form, point-slope form, and general linear form are the three most common forms. The first section focuses on slope-intercept form: it explains how to write an equation of a line in slope-intercept form, given a graph of that line. The second section explains how to write an equation of a line in point-slope form, and the third section explains how to write an equation of a line in general linear from.

The fourth section discusses other, perhaps less common, forms of linear equations. In particular, it shows how to write equations of horizontal and vertical lines.

The final section explains how to convert among forms of linear equations. Different forms have different uses, and the given form of an equation might not always be the most useful. Thus, it is important to know how to convert an equation to a form that will serve the intended purpose.

Learning how to write equations from graphs is the next logical step after learning how to create graphs from equations. After mastering the material in this chapter, you will be able to switch back and forth between the equation of a line and the graph of that line.

Writing equations from graphs is an especially useful tool for scientists. Scientists often gather data from experiments, graph it, and search for an equation to describe the trend they see.