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Finding the Equation of a Line from Its Graph

Suppose you are given the graph of a line in the coordinate plane, and asked to find its equation.

If you can find the y-intercept and the slope, you can write the equation in slope-intercept form (unless, of course, it's a vertical line.)

Here the line crosses the y-axis at –3, so the y-intercept is –3.

To find the slope, use the two points (–6, 0) and (0, –3) and substitute these in the slope formula: