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Alpha Teach Yourself Algebra I in 24 Hours by Jane Cook

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Hour 16
Equations with Two Variables: Equations of Lines
Last hour’s graphing of points and lines from equations with an x and a y variable showed you one way to find many ordered pairs that are true for a given equation. Plotting the intercepts allowed you to draw the line that contains each equation’s solutions.
 
This hour you will learn how to use a line’s slope and key points to write that line’s equation—in some ways, the reverse of the process you learned last hour—along with how to solve real-life problems about direct and inverse variation.

Finding the Equation of a Line from the Slope and y-Intercept

The graph of the equation y - 2x = 6 follows. When x = 0, y = 6, and when y = 0, x = -3. These two key points are the ordered pairs ...

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