First, solve the equation for y.
y = 3x - 9
This is slope-intercept form, and the y-intercept is (0,-9).
Find the x-intercept by substituting 0 for y and solving for x.
(0) = 3x - 9
9 = 3x
3 = x
Thus the x-intercept is (3,0).
Plot the two points and draw a line that contains them both.
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You could have also just substituted any two values for x and solved for their associated ys, plotted those two points and connected them.
3x - y = 9
for x=0 3(0) - y = 9
y= -9 ∴(0,-9)
3(1) - y = 9
3 - y = 9
-y = 6
y = -6 ∴ (1,-6)
Either method gets you the answer quickly. The first has the virtue of producing the slope intercept form of the equation which also tells you the slope of the graph should you also want that.
