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View Full Version : How to do inequality problems


yaya12
Dec 9, 2009, 05:30 PM
-8|9+9m| < 72

Perito
Dec 9, 2009, 08:34 PM
is the "|" an absolute value sign? I'm not sure whether to interpret that as what I've written below, or not.

-8 \left( |9+9m| \right) \, \le \, 72

In any inequality, you plot or calculate the curve corresponding to the "=" case. Then, pick a point above or below the curve and determine if it meets the inequality (< in this case). If it doesn't, try the other side (one side has to work). Then, you include all the area.

If the inequality is < or >, the inequality doesn't include the curve.

mathwiz3502
Dec 10, 2009, 04:15 PM
First divide by -8 on both sides
Now take away the abs. value symbol but have the opposite side be negative and positive, two equations may help.
Now solve.

InfoJunkie4Life
Dec 13, 2009, 01:14 PM
Isn't there some rule, if you multiply by a negative, you have to switch the orientation of the inequality?