Graphing Lines
Equations of the form axþby¼c where a, b, and c are real numbers are
calledlinear equations in two variablesand their graphs are straight lines.
In order to graph a linear equation, find the coordinates of two points on the
line (i.e., solutions), and then plot the points and draw the line through the two
points.EXAMPLE
Draw the graph of xþy¼6.SOLUTION
Select two values for x and find the corresponding y values:
Let x¼ 3 Let x¼ 5
xþy¼6xþy¼ 6
3 þy¼ 65 þy¼ 6
3 3 þy¼ 6 35 5 þy¼ 6 5
y¼3y¼ 1
(3, 3) (5, 1)
Plot the points and draw a line through the two points (see Fig. 11-7).210 CHAPTER 11 Graphing
Fig. 11-7.