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Question 36114: one question please
when graphing a linear inequality how do we know if the inequality represents the area above the line.
Answer by ilana(307)   (Show Source):
You can put this solution on YOUR website! 2 ways:
If the inequality is of the form y>mx+b, it is the area above the line, if it is y(less than)mx+b, it is the area below. A method that will work regardless of the form of the inequality is to test points above or below. For example if I have 9x+3y>6, I draw the (dotted) line with slope -3 and y-intercept 2. I then test any point not on the line, so (0,0) is usually a nice simple choice. 9(0)+3(0)=0, which is not >6, so (0,0) is not in the shaded region. So the area above the line is shaded.
Note, if we wrote this inequality in slope-intercept form, we'd have y>-3x+2, so also by our first method the area above the line is shaded.
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