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March 25th, 2017, 01:09 PM   #1
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really basic question about functions

So I recently started a highschool level math course (in my spare time, so without any teachers) on top of my high school studies,

On one of the exercises, they gave me a function,

h(x) = -|2x-5|

I have never seen brackets like this | before. I'm required to solve a bunch of things (zero, min/max. etc., really easy stuff still). I'm required to use the TI-84 plus calculater (Texas Instruments) to solve this.

So first of all I have to fill in this function in y=.

But I don't know how to input brackets like | and whether I can also get the same result by using normal brackets ().

could anyone tell me how to input those special brackets in a calculator and what the difference is between || and ()?

Thank you for your time at least.

Last edited by skipjack; March 25th, 2017 at 05:22 PM.
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March 25th, 2017, 01:13 PM   #2
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$|x|$ is referred to as the "absolute value" of $x$

You can think of it as stripping away the negative sign.

$|x| = \begin{cases} 0 &x=0 \\ -x &x < 0 \\ x &0 < x \end{cases}$

some info on using the absolute value on your calculator

Last edited by romsek; March 25th, 2017 at 01:23 PM.
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March 25th, 2017, 01:20 PM   #3
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woa thanks that really helped me!

There was no info about it in my handbook at all. now the result looks way more realistic.
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March 25th, 2017, 01:39 PM   #4
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it is also written abs(x) in some places such as computers.

Another name is the modulus or mod(x)

You can get the vertical line symbol with the shift key and the key to the right of the z key on a computer keyboard. Thus |

Go well in your studies and if in doubt ask.

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March 25th, 2017, 02:09 PM   #5
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Another way is

$|x| = \sqrt{x^2}.$

Means the exact same thing as what Romsek said, but it is very easy to compute on a calculator.
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March 25th, 2017, 03:48 PM   #6
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@studiot
okay didn't know about the alternative naming of mod(x)
the keyboard shortcut doesnt work for me though since i don't have the qwerty layout
tough i know how to get | it using my pc.

The course i'm following is really bad on some parts since it gives you 4 pages of information and 2 pages of practice excercises which i all get but then theyl just base the excercises on grades on things that aren't in the book and that i haven't ever seen before. will be a serious struggle but i'l do my very best to get through it.

@JeffM1
I see it somehow makes sence since you eliminate the - by making it a square root. Though honestly i couldnt possibly guess that before since i had |absolutely| no idea what the brackets did (pun intended)
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