Everytime you have a variable inside an absolute value and an inequality, you'll branch off into two other inequalities. In general, if |y| < a (for some positive value a), then the inequality translates to
-a < y < a
In your case, since |x + 3| < 5, then
-5 < x + 3 < 5
And if we subtract 3 from all parts of the inequality, we get
-8 < x < 2
or, x is in the interval (-8,2)
Meaning x lies strictly between -8 and 2.
As a side note, when you have absolute value with equations, i.e.
|x + 3| = 5
which becomes
x + 3 = 5 and x + 3 = -5
x = 2 , x = -8
Therefore, x = {2, -8}
Secondary side note: if the absolute value of x + 3 is GREATER than 5, then we get an OR instead of an AND. Note that earlier, when |x+3| < 5, then we get an AND;
(x + 3 < 5) AND (-5 < (x + 3))
In the case of a greater sign, i.e. |x + 3| > 5, then
x + 3 > 5 OR x + 3 < -5
Therefore
x > 2 OR x < -8
and our interval is
x in the interval (-infinity, -8) U (2, infinity)
BOTTOM LINE: If you have an absolute value with an inequality and it's LESS than, it's an AND, i.e. |y| < a means (-a < y) AND (y < a).
If you have an absolute value with an inequality and it's MORE than, it's an OR: |y| > a implies (y > a) OR (y < -a).
2006-12-26 09:25:12
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answer #1
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answered by Puggy 7
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*You have two inequalities: x + 3 < 5 and x + 3 > -5
1. solve the first inequality:
x + 3 < 5
First: subtract 3 from both sides:
x + 3 - 3 < 5 - 3
x < 2
2. solve the second inequality:
x + 3 > -5
x + 3 - 3 > -5 - 3
x > -8
answers: x < 2 and x > -8
2006-12-26 09:21:50
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answer #2
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answered by ♪♥Annie♥♪ 6
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this means that both of the following apply:
x + 3 < 5, and
-x - 3 <5
solve by isolating x:
x < 2
-x < 8, which means x > -8
-8 < x < 2 (x is between -8 and 2)
2006-12-26 09:22:52
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answer #3
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answered by car of boat 4
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