abs value

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Ray3Ray3

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Jul 13, 2009
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hi i have some questions about absolute value. i have the definition of absolute value as: the absolute value of a is a if a>=0, and is -a, if a<0. so a question on my homework has a bunch of parts...they start out simple, but i started to get tripped up

av(a) if a<0= -a ?
av(-a) if a<0= a ?
-av(a) if a>0= a ????
-av(-a) if a<0= a ????
av(x-2), if x<2= ??????????????????

I dont understand how to do the last one, but i am not sure if i fully understand the definition, so i dont know if my answers are right for the others, can you please shed some light on this for me...please

Thanks
Ray
 
ok nobody seems to want to jump on this...

i think absval (a) if a<0 = -a
i think absval (-a) if a<0 = a
i think -absval(a) if a>0 = -a
i think -absval(-a) if a<0 = -a
i figured out that absval(x-2) if x<2 = -(x-2)

Any insight would be very helpful
 
Denis said:
Ray3Ray3 said:
i have the definition of absolute value as: the absolute value of a is a if a>=0, and is -a, if a<0.
Click to expand...
NO!! Absolute value of a is ALWAYS a !
http://en.wikipedia.org/wiki/Absolute_value

By the way, we're not here hanging around waiting for questions, ready to "jump in".
This is a free site, so don't expect miracles :shock:
Click to expand...

Actually the original sentence is correct the absolute value of a is -a, if a<0.

absval(-2) <> -2
absval(-2) = -(-2) = 2

On to the problems:
av(a) if a<0= -a Correct
av(-a) if a<0= a Correct
-av(a) if a>0= a Wrong: The av(a) if a>0 is a, but then you are negeting that, so the answer is -a
-av(-a) if a<0= a Correct
av(x-2), if x<2= If X = 2 then av(X-2) = 0. The answer is -(X-2)
 
Sometimes it helps to plug in actual numbers that fit the problem, to see what the outcome is.

>av(x-2), if x<2= ??????????????????

If x<2 then |x-2| ????

1 is < 2. So plug it in and evaluate. |1-2| = |-1| = +1.
0 is < 2. |0-2| = |-2| = +2.
-1 is < 2. |-1-2| = |-3| = +3.

It appears that we always get a positive result.
Maybe I'm missing something.
 
Loren said:
Sometimes it helps to plug in actual numbers that fit the problem, to see what the outcome is.

>av(x-2), if x<2= ??????????????????

If x<2 then |x-2| ????

1 is < 2. So plug it in and evaluate. |1-2| = |-1| = +1.
0 is < 2. |0-2| = |-2| = +2.
-1 is < 2. |-1-2| = |-3| = +3.

It appears that we always get a positive result.
Maybe I'm missing something.
Click to expand...

You are correct they answers will be positive.

X = 1. |X-2| = |1-2| = |-1| = +1. -(X -2) = -(1 - 2) = -(-1) = +1
X = 0. |X-2| = |0-2| = |-2| = +2. -(X -2) = -(0 - 2) = -(-2) = +2
X = -1. |X-2| = |-1-2| = |-3| = +3. -(X -2) = -(-1 - 2) = -(-3) = +3
 
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