To graph the inequality, we have to draw the boundary line. The equation of a boundary line is written by replacing the inequality symbol from the inequality with an equals sign.
Inequality &
Boundary Line
y ≤ -4 x+12 &
y = -4 x+12
Fortunately, this equation is already in slope-intercept form, so we can identify the slope m and y-intercept (0, b).
y= -4x+ 12
We will plot the y-intercept (0, 12), then use the slope m= -4 to plot another point on the line. Connecting these points with a solid line will give us the boundary line of our inequality. Note that the boundary line is solid, not dashed, because the inequality is notstrict.
Shading the Plane
To decide which side of the boundary line to shade, we will substitute a test point that is not on the boundary line into the given inequality. If the substitution creates a true statement, we shade the region that includes the test point. Otherwise, we shade the opposite region. Let's use (0,0) as our test point.
