You are watching: Do you flip the inequality sign when multiplying by a negative number
Operating v Inequalities: multiply & Dividing
Performing multiplication or division with one inequality is practically identical to multiplying or separating parts of traditional equations (with one exception, covered below).
Consider the adhering to examples:
The Exception: an adverse Numbers
There is one really important exemption to the ascendancy that multiplying or splitting an inequality is the very same as multiplying or separating an equation.
Whenever you multiply or divide an inequality through a an unfavorable number, you have to flip the inequality sign.
In the adhering to example, notification how the sign once the inequality is split by -2
In the adhering to example, notice how the sign becomes a > sign once the inequality is split by -2
-2x + 15 3-2x + 15 - 15 3 - 15-2x -12x > 6
Warning: Caution once Multiplying or dividing Variables
One really important implicit of this ascendancy is: girlfriend cannot divide by an unknown (i.e., a variable) uneven you are sure the its sign because you do not know whether you must flip the authorize of the inequality. There room plenty that instances wherein you will recognize the sign of a variable and also as a result, you have the right to multiply or divide and also know for certain whether you must flip the inequality sign. However, you must constantly ask you yourself whether you understand for sure the sign of the variable before dividing or multiply when taking care of an inequality.
If 2x5y 10y, what is the variety of potential worths for x?You cannot divide by y or 5y since you do not recognize whether y is negative or optimistic and, together such, you execute not know whether to flip the inequality.
Just as it is possible to resolve two simultaneous equations, so the is possible to resolve two inequalities (or three, or four, etc.). In fixing multiple simultaneously inequalities using multiplication or division, the most important component is to solve each inequality separately and then incorporate them.
If 2x 150, what is the range of possible values because that x?1.) solve each inequality alone.2x x -5x x > 2
For numerous students, the above collection of inequalities can finest be understood graphically. The equipment to the collection of inequalities is the overlapping graphical area.
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