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Unformatted text preview: Not much to this one. We’ll proceed as we’ve done the previous two. 14 < 21x  14 < 1
0 < 21x < 15
Don’t get excited about the fact that one of the sides is now zero. This isn’t a problem. Again, as
with the last part, we’ll be dividing by a negative number and so don’t forget to switch the
direction of the inequalities. 15
21
5
0> x>7
0> x> OR  5
<x<0
7 Either of the inequalities in the second row will work for the solution. The interval notation of æ5
è7 ö
ø the solution is ç  , 0 ÷ .
[Return to Problems] When solving double inequalities make sure to pay attention to the inequalities that are in the
original problem. One of the more common mistakes here is to start with a problem in which one
of the inequalities is < or > and the other is £ or ³ , as we had in the first two parts of the
previous example, and then by the final answer they are both < or > or they are both £ or ³ . In
other words, it is easy to all of a sudden make both of the inequalities the same. Be careful with
this.
There is o...
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 Spring '12
 MrVinh

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