Saturday, November 27, 2010

For what x the inequality is true 2(x-1/2)(x+2)

We'll divide both sides by
2:


Since the value is positive, teh inequality still
holds:


(x -
1/2)(x+2)<0


We'll conclude that a product is
negative if the factors are of opposite sign.


There are 2
cases of study:


1)  (x - 1/2) <
0


and


      (x+2) >
0


We'll solve the first inequality. For this reason, we'll
isolate x to the left side.


x <
1/2


We'll solve  the 2nd
inequality:


    (x+2) >
0


We'll subtract 2 both
sides:


x > -2


The
common solution of the first system of inequalities is the interval (-2 ,
1/2).


We'll solve the second system of
inequalities:


2)  (x-1/2) >
0


and


      (x+2) <
0


x-1/2 > 0


x >
1/2


     (x+2) < 0


x
< -2


Since we don't have a common interval to satisy
both inequalities, we don't have a solution for the 2nd
case.


So, the complete solution is the
solution from the first system of inequalities, namely the interval (-2 ,
1/2).

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