Writing Linear Equations Using Graphs

Students learn to write the equation of a line in slope-intercept form using the graph of the line. In some problems, the graph is given, and in other problems, the graph must be drawn (using given information about points and slope). Since slope intercept form is the same thing as y = mx + b form, where m represents the slope and b represents the y-intercept, the next step is to use the graph to find the slope and y-intercept of the line. To find the slope, use the ratio rise over run between any two points on the given line. To find the y-intercept, remember that the y-intercept is the point where the line crosses the y-axis. Finally, substitute the values for the slope, m, and y-intercept, b, into the formula y = mx + b to write the equation of the line.