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#1 2010-09-28 08:04:41

misheeru
Member
Registered: 2010-02-18
Posts: 4,594

Equations with parenthesis?

Hey guys, so we started doing some "simple" equations in math and I'm totally lost on some of these!

First off, I get the easier ones like:

5x + 2 = 12 (answer: x = 2)

or

6x - 8 = 16 (answer: x = 4)


But I'm having trouble solving for x in the more complicated ones like:

3(x + 2) = 16

7(2x + 6) = 1

or

4(3 - 2x) = 15



please help! I don't get these ones at all! Thanks!


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#2 2010-09-28 08:06:17

bobbym
bumpkin
From: Bumpkinland
Registered: 2009-04-12
Posts: 109,606

Re: Equations with parenthesis?

Hi;

3(x + 2) = 16

Expand them out first.

3x + 6 = 16

Now you know how!


In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

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#3 2010-09-28 08:15:44

misheeru
Member
Registered: 2010-02-18
Posts: 4,594

Re: Equations with parenthesis?

But since 3 doesn't go into 14 wouldn't out answer end up being a decimal?


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#4 2010-09-28 08:16:24

bobbym
bumpkin
From: Bumpkinland
Registered: 2009-04-12
Posts: 109,606

Re: Equations with parenthesis?

Where does th 14 come from?


In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

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#5 2010-09-28 08:23:58

misheeru
Member
Registered: 2010-02-18
Posts: 4,594

Re: Equations with parenthesis?

Like this?


3x + 2 = 16
     - 2     -2

3x = 14

then I'm supposed to go on from there? Thats where 14 came from...


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#6 2010-09-28 08:25:45

bobbym
bumpkin
From: Bumpkinland
Registered: 2009-04-12
Posts: 109,606

Re: Equations with parenthesis?

Nope!

3(x + 2) = 16

3x + 6 not 3x + 2


In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

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#7 2010-09-28 08:32:26

misheeru
Member
Registered: 2010-02-18
Posts: 4,594

Re: Equations with parenthesis?

Oh, i missed that!

so then from there we go to...?

3x + 6 = 16
     - 6   - 6

to 3x = 10?

am i good so far???


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#8 2010-09-28 08:34:30

bobbym
bumpkin
From: Bumpkinland
Registered: 2009-04-12
Posts: 109,606

Re: Equations with parenthesis?

Yes, when you multiply something that is in a parentheses you multiply everything.

3x = 10 is right but you have not solved for x.


In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

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#9 2010-09-28 08:39:03

misheeru
Member
Registered: 2010-02-18
Posts: 4,594

Re: Equations with parenthesis?

I know that. I was asking you if I had done it correctly so far.

Aren't we still going to end up with a decimal because 3 doesn't go into 10 evenly?


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#10 2010-09-28 08:41:45

bobbym
bumpkin
From: Bumpkinland
Registered: 2009-04-12
Posts: 109,606

Re: Equations with parenthesis?

Nope.

Rant:

I do not like the modern reptilian trend of eliminating fractions in place of decimals. This teaching startegy is so silly and from the standpoint of numerical analysis, funny.

End Rant:

You will end up with a beautiful fraction!!


In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

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#11 2010-09-28 08:45:26

misheeru
Member
Registered: 2010-02-18
Posts: 4,594

Re: Equations with parenthesis?

YUCK!

And you are going to be mad at me, when I tell you I just went back in my notes and checked and I copied the problem wrong to begin with.


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#12 2010-09-28 08:47:30

bobbym
bumpkin
From: Bumpkinland
Registered: 2009-04-12
Posts: 109,606

Re: Equations with parenthesis?

Nope, copying a problem is my biggest problem. I understand other people's mistakes because I make them all.

We will start with the new problem if you like.


In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

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#13 2010-09-28 08:56:57

misheeru
Member
Registered: 2010-02-18
Posts: 4,594

Re: Equations with parenthesis?

lol, okay thanks.

here is the real problem:

3(x + 2) = 6  (i really have no idea where i got 12 from)

okay so let me try this:

3(x + 2) = 6

3x + 6 = 6
      - 6  - 6
3x = 0

x = 0

how does that look?


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#14 2010-09-28 08:58:28

bobbym
bumpkin
From: Bumpkinland
Registered: 2009-04-12
Posts: 109,606

Re: Equations with parenthesis?

That is correct. But too easy! Did your teacher provide that problem?


In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

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#15 2010-09-28 09:18:35

misheeru
Member
Registered: 2010-02-18
Posts: 4,594

Re: Equations with parenthesis?

No, its part of the assignment. Now that I know what I'm doing it is pretty easy.

What about this one:

5(x - 4) = 12

5x - 9 = 12
     +9   +9

5x = 21

okay, so i can just tell we are going to end up with some crummy fraction... what do i do from here?


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#16 2010-09-28 09:29:50

bobbym
bumpkin
From: Bumpkinland
Registered: 2009-04-12
Posts: 109,606

Re: Equations with parenthesis?

Ho!

5(x - 4) = 12

5x - 9 = 12

Mind expanding 5(x-4) again. please.


In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

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#17 2010-09-28 09:31:55

misheeru
Member
Registered: 2010-02-18
Posts: 4,594

Re: Equations with parenthesis?

what do you mean?

5x - 9 = 12

that?


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#18 2010-09-28 09:34:00

bobbym
bumpkin
From: Bumpkinland
Registered: 2009-04-12
Posts: 109,606

Re: Equations with parenthesis?

5(x-4) ≠ 5x - 9

That up there is saying they do not equal each other. You must multiply everything in the parentheses, remember?


In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

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#19 2010-09-28 09:36:02

misheeru
Member
Registered: 2010-02-18
Posts: 4,594

Re: Equations with parenthesis?

opps i added instead of multiplying.

so its

5x - 20?


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#20 2010-09-28 09:38:17

bobbym
bumpkin
From: Bumpkinland
Registered: 2009-04-12
Posts: 109,606

Re: Equations with parenthesis?

Yes,

5x - 20 = 12 Now you should be an expert on what comes next.


In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

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#21 2010-09-28 09:44:37

misheeru
Member
Registered: 2010-02-18
Posts: 4,594

Re: Equations with parenthesis?

expert my.....

5x - 20 = 12
     +20 +20

1/5 * 5x = 32 * 1/5

= 32/5?

Last edited by misheeru (2010-09-28 09:45:18)


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#22 2010-09-28 09:51:04

bobbym
bumpkin
From: Bumpkinland
Registered: 2009-04-12
Posts: 109,606

Re: Equations with parenthesis?

That's right, if you want to leave it as an improper fraction.


In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

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#23 2010-09-28 09:52:29

misheeru
Member
Registered: 2010-02-18
Posts: 4,594

Re: Equations with parenthesis?

yeah, it should be a mixed number right?

in forgot how to do that...uh isn't it something like you decide and the leftover becomes the bog number? Or something along those lines??


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#24 2010-09-28 10:00:28

bobbym
bumpkin
From: Bumpkinland
Registered: 2009-04-12
Posts: 109,606

Re: Equations with parenthesis?

Something like that. Want to see how?


In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

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#25 2010-09-28 10:06:07

misheeru
Member
Registered: 2010-02-18
Posts: 4,594

Re: Equations with parenthesis?

yes, please.


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