Thursday, October 2, 2014

find x values if l 2x -5 l + 7

To find values of the inequality |2x-5| < 10
.


We know that |x-n| = x-n ix x >n and  |x-n| = n-x if
x< n.


Therefore |2x-5| = 2x-5 for 2x-5 > 0. Or x
> 5/2.


Therefore or x > 5/2 , |2x-5| < 10 
implies 2x-5 < 10


2x-5 < 10 implies 2x-5+5 <
10+5 , as  we added equals to both side.


2x <
15.


2x < 15 implies x < 15/2 = 7.5 , as we divided
 both sides by positive equals.


Therefore x>2.5
, x < 7.5.



When x < 2.5 ,
|2x-5| < 10 implies 5-2x < 10.


We add 2x to both
sides:


5 < 10 +2x.


5-10 <
10+2x-10.


-5 < 2x


-5/2 <
2x/2


-2.5 < x. Or x >
-2.5.


Therefore  x  < -2.5 for any x <
=2.5.


Therefore x  is in the interval
(-2.5 , 7.5} but the strict inequality does allow  x  to take boundary
values.

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