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today in class we were working on Abosluote Value Equations  and i need help with these

1. absolute value of 2x+5=3x+4

2. 4 then absloute value 3x+4=4x+8

3. one half absolute value 3c+5=6c+4

4. two thirds absolute value 3x-6=4(x-2)

5. absolute value 2z-3=4z-1

Can someone please help me with these i have no idea how to do them i tried them all and i have no idea whatsoever...

 Aug 12, 2015

Best Answer 

 #2
avatar+118608 
+15

3. one half absolute value 3c+5=6c+4

 

$$\\3.\\\\
\frac{1}{2}|3c+5|=6c+4\\\\
|3c+5|=2(6c+4)\\\\
2(6c+4)=|3c+5|\\\\
12c+8=|3c+5|\\\\
$now it is very similar to question 2$$$

 

You should be able to have a go at 4 and 5 by yourself now.

Let us know if this is still a problem.  Or put your answer up and we can check it for you :)

 Aug 12, 2015
 #1
avatar+118608 
+15

Hi Knk98  

 

1) 2x=5= 3x+4      There are 2 equal sign so you better correct this one.

 

2) 

4*|3x+4|=4x+8

4*|3x+4|=4(x+2)

|3x+4|=x+2                I have divided both sides by 4

x+2=|3x+4|                Now think for a momement  |6|=|-(6)|   so    |3x+4| = |-(3x+x)|

hence

x+2=3x+4       or      x+2=-(3x+4)

    2= 2x+4      or      x+2= -3x-4

    -2=2x          or        4x+2=-4

    -1=x           or        4x=-6

     x=-1          or          x=-6/4 = -3/2

   x=-1           or          x=3/2

These are the 2 answers.   

 Aug 12, 2015
 #2
avatar+118608 
+15
Best Answer

3. one half absolute value 3c+5=6c+4

 

$$\\3.\\\\
\frac{1}{2}|3c+5|=6c+4\\\\
|3c+5|=2(6c+4)\\\\
2(6c+4)=|3c+5|\\\\
12c+8=|3c+5|\\\\
$now it is very similar to question 2$$$

 

You should be able to have a go at 4 and 5 by yourself now.

Let us know if this is still a problem.  Or put your answer up and we can check it for you :)

Melody Aug 12, 2015
 #3
avatar+143 
+10

on questoin 2 would you not distribute the 4(x+2) and get 4x+8

 Aug 13, 2015
 #4
avatar+118608 
+10

4*|3x+4|=4x+8

 

on questoin 2 would you not distribute the 4(x+2) and get 4x+8

It is really good that you are asking questions Knk98.    

 

It was already 4x+8 at the very beginning.

I saw that the Left hand side (LHS)  was    4*an absolute value experssion.

If I could factor 4 out of the RHS then I could divide both sides by 4 and the 4s would just go away makeing the equation more simple.

4*|3x+4|=4x+8

4*|3x+4|=4*(x+2)      Now I can divide both sides by 4

$$\\\frac{4*|3x+4|}{4}=\frac{4*(x+2)}{4} \\\\
$Now the 4s can cancel out$\\\\
\frac{\not{4}*|3x+4|}{\not{4}}=\frac{\not{4}*(x+2)}{\not{4}} \\\\
$This will leave me with$\\\\
|3x+4|=x+2\\\\
$I like to swap sides here but it is not really necessary$\\\\
x+2=|3x+4|\\\\
$Now remember how $|2|=|-2|\;\;\; well\\\\
|3x+4|=|-(3x+4)| \qquad too.\\\\
so\\
3x+4=x+2\qquad or \qquad 3x+4=-(x+2)\\\\$$

 

I finished it before.

If you have any more questions please ask and I will try to explain some more.

 

It is possible that your real problem is not with absolute equations but just with equations in general.

It is important that you try to isolate the source of your problems then you will know what you need to work on.      

 Aug 13, 2015
 #5
avatar+143 
+10

Thanks this really helped me... Now i know what im doin Thanks Melody

 Aug 13, 2015
 #6
avatar
+5

Solve    | x2– 4x – 5 | = 7

 Aug 14, 2015
 #7
avatar+118608 
+10

 | x2– 4x – 5 | = 7

 

x2– 4x – 5  = +7    OR      x2– 4x – 5  = -7

x2– 4x – 12 = 0     OR      x2– 4x +2 = 0

Now use the quadratic formula with each one to get the answers.  There are 4 answers :)

 Aug 15, 2015

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