Graphing absolute value inequalities

**jscalalamoboy** · October 4th 2009, 10:51 AM

I've reached a standstill on my math homework, can someone explain how to do this? I'll post one of my questions and if possible can you show me the graph and how you would reach that point? I'd appreciate it. Also can you explain what each part of the equation means?

$f(x)=3-|x-2|$

What would it change if that $3$ was a fraction such as $1/2$ ?

What about if there was a number after it being added? Subtracted?

Okay that answers all my basic questions. Thanks for your help!

**james_bond** · October 4th 2009, 11:05 AM

See this. Can you graph $3-(x-2)$ and $3+(x-2)$ ? When you want to plot functions with absolute values you should consider different cases. You should see that if $x>2$ then you can leave the absolute value and if $x<2$ then $|x-2|=-(x-2)$ . Maybe you can take a look at this as well.
To your questions: there is no basic difference in the graphing method if you change 3 or equivalently add/subtract numbers to/from it. You can try plotting in WolframAlpha.

**jscalalamoboy** · October 4th 2009, 11:12 AM

Originally Posted by james_bond

See this. Can you graph $3-(x-2)$ and $3+(x-2)$ ? When you want to plot functions with absolute values you should consider different cases. You should see that if $x>2$ then you can leave the absolute value and if $x<2$ then $|x-2|=-(x-2)$ . Maybe you can take a look at this as well.
To your questions: there no basic difference in the graphing method if you change 3 or equivalently add/subtract numbers to/from it. You can try plotting in WolframAlpha.

Wolfram should be excessively helpful for the rest of this year

but let me take a second to understand, you just make an input output system and using the absolute value it should eventually make a V shape... hard to describe but... I think I get it. Hm.

**e^(i*pi)** · October 4th 2009, 11:15 AM

Originally Posted by jscalalamoboy

I've reached a standstill on my math homework, can someone explain how to do this? I'll post one of my questions and if possible can you show me the graph and how you would reach that point? I'd appreciate it. Also can you explain what each part of the equation means?

$f(x)=3-|x-2|$

What would it change if that $3$ was a fraction such as $1/2$ ?

What about if there was a number after it being added? Subtracted?

Okay that answers all my basic questions. Thanks for your help!

It should be easier to plot the graph of -|x| (reflect |x| in the x axis blue line) and then move it two units to the right on the x axis (green line).

Finally move it 3 up on the y axis (red line)

**jscalalamoboy** · October 4th 2009, 11:26 AM

Originally Posted by e^(i*pi)

It should be easier to plot the graph of -|x| (reflect |x| in the x axis blue line) and then move it two units to the right on the x axis (green line).

Finally move it 3 up on the y axis (red line)

That's how the teacher explained it. I'll remember that, thanks. Haha, you're using Linux! What kind? I got UBUNTU and Grub wiped itself off my PC, so I have to use my Mac for now until I can find my Livedisk... Anyways, is there any possible way to get KM Plot on a Mac and how much does KM Plot cost?

**e^(i*pi)** · October 4th 2009, 11:36 AM

Originally Posted by jscalalamoboy

That's how the teacher explained it. I'll remember that, thanks. Haha, you're using Linux! What kind? I got UBUNTU and Grub wiped itself off my PC, so I have to use my Mac for now until I can find my Livedisk... Anyways, is there any possible way to get KM Plot on a Mac and how much does KM Plot cost?

I use Arch+KDEmod

You may be able to get KmPlot as part of the KDE suite for mac but it's likely to end up being bloated and not really worth it. May be better to find the live disk first

. Also KmPlot is free as in both speech and beer

**jscalalamoboy** · October 4th 2009, 11:39 AM

Originally Posted by e^(i*pi)

I use Arch+KDEmod

You may be able to get KmPlot as part of the KDE suite for mac but it's likely to end up being bloated and not really worth it. May be better to find the live disk first

. Also KmPlot is free as in both speech and beer

Yeah every time I boot up I get a GRUB error that says it can't find the disk.

**e^(i*pi)** · October 4th 2009, 11:41 AM

Originally Posted by jscalalamoboy

Yeah every time I boot up I get a GRUB error that says it can't find the disk.

Chances are you removed the partition grub part 2 was residing on. Nonetheless to avoid spamming this thread it would be better to continue via PM or VM

**jscalalamoboy** · October 4th 2009, 11:42 AM

Originally Posted by e^(i*pi)

Chances are you removed the partition grub part 2 was residing on. Nonetheless to avoid spamming this thread it would be better to continue via PM or VM

Okay thanks for your help anyway! I finished that part of my homework now. Test on Monday.

"Is the ordered pair $(2,-1)$ a solution for the inequality $5x-3y$ < $-10$ ?"

I just put $2$ in for $x$ and $-1$ in for $y$ , correct?

**e^(i*pi)** · October 4th 2009, 11:52 AM

Originally Posted by jscalalamoboy

Okay thanks for your help anyway! I finished that part of my homework now. Test on Monday.

"Is the ordered pair $(2,-1)$ a solution for the inequality $5x-3y$ < $-10$ ?"

I just put $2$ in for $x$ and $-1$ in for $y$ , correct?

Yes you do.

I make it that the ordered pair is not a solution

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