I'm getting confused....

C

CalebsMomma

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Jul 13, 2009
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So I have this problem that reads like this:

2x^2-7x-3x+2x=1+2x

So I know that I need to get to the point to make it equal zero on the right side, and add like terms which leaves me with:

2x^2-7x-4=0

So here's where I get confused, I already had a problem that filtered out exactly the same as state above....but when I plug in the answers that could stand for x, being -1/2 and 4. It is not true in this case. And I have worked out both problems as follows:

(2x+1)(x-4)=0
2x+1=0
x=-1/2

x-4=0
x=4

When I plug in -1/2, I end up with 15/2=0
When I plug in 4, I end up with 5=9

PLEASE can someone tell me what I am doing wrong?
 
CalebsMomma said:
So I have this problem that reads like this:

2x^2-7x-3x+2x=1+2x

So I know that I need to get to the point to make it equal zero on the right side, and add like terms which leaves me with:

2x^2-7x-4=0---> how did you get that---- incorrect

So here's where I get confused, I already had a problem that filtered out exactly the same as state above....but when I plug in the answers that could stand for x, being -1/2 and 4. It is not true in this case. And I have worked out both problems as follows:

(2x+1)(x-4)=0
2x+1=0
x=-1/2

x-4=0
x=4

When I plug in -1/2, I end up with 15/2=0
When I plug in 4, I end up with 5=9

PLEASE can someone tell me what I am doing wrong?
Click to expand...
 
MY APOLOGIES I have been lookin at this darn thing all night and it's not 3x, it's just 3, so it should read

2x^2-7x-3+2x=1+2x

Which then turns into

2x^2-7x-4=0

Thanks for catching that!!!
 
Hint :

\(\displaystyle x = \frac{1}{2}\)

Or


\(\displaystyle x = - 4\)
 
Ok, but it doesn't factor out to be -4 and +1/2? How did you get it there...
Here is what I have....

2x^2-7x-3+2x=1+2x

2x^2-5x-3-1-2x=0

2x^2-7x-4=0

(2x+1)(x-4)=0

2x+1=0
x=-1/2

x-4=0
x=4
 
CalebsMomma said:
Ok, but it doesn't factor out to be -4 and +1/2? How did you get it there...
Click to expand...

Yeah, it's the same ... it's multiplication :: got it ??
 
No, I don't, I know I may be goofy, but it doesn't make sense, I have tried flip floppin it anyway I can imagine, but I don't see how it can come out the same?? :?
 
CalebsMomma said:
When I plug in -1/2, I end up with 15/2=0
When I plug in 4, I end up with 5=9
Click to expand...


No you dont,Actually you find the values of x in which the equation equals to ZERO .

\(\displaystyle (2x + 1)(x - 4) = 0\)

\(\displaystyle ( 2(\frac{-1}{2}) + 1 )(\frac{1}{2} - 4)\)

\(\displaystyle ( -1 + 1 )( \frac{-7}{2} )\)

\(\displaystyle ( 0 )(\frac{-7}{2} ) = 0\)Surely..

Try the value 4 by yourself, I think you got the idea .
 
:wink: YOU ARE A DOLL!!!! THANKS A TON!!!! You were right, it did work, I was just simply making a simple error! I was multiplying the 2 and the -1/2 and then adding the 1 instead of adding the 1 and the -1/2 and then multiplying!!! Thanks so much!!!
 
CalebsMomma said:
:wink: YOU ARE A DOLL!!!! THANKS A TON!!!! You were right, it did work, I was just simply making a simple error! I was multiplying the 2 and the -1/2 and then adding the 1 instead of adding the 1 and the -1/2 and then multiplying!!! Thanks so much!!!
Click to expand...

You're welcomed Momma, I do love Kg's instead of TONS :) .
 
Momma is CORRECT Aladdin: x = 4 or x = -1/2 ; -4 and 1/2 is not correct. Good work Big Momma :wink:

2x^2 - 7x - 4 = 0

x = 4: 2(4^2) - 7(4) - 4 = 32 - 28 - 4 = 0

x = -1/2: 2((-1/2)^2) - 7(-1/2) - 4 = 1/2 + 7/2 - 4 = 0
 
Denis said:
Momma is CORRECT Aladdin: x = 4 or x = -1/2 ; -4 and 1/2 is not correct. Good work Big Momma :wink:

2x^2 - 7x - 4 = 0

x = 4: 2(4^2) - 7(4) - 4 = 32 - 28 - 4 = 0

x = -1/2: 2((-1/2)^2) - 7(-1/2) - 4 = 1/2 + 7/2 - 4 = 0
Click to expand...


Yes , you're right Denis. I made big mistak by taking (2x-1)(x+4) instead of taking (2x+1)(x-4)

because, if yo expand the first one(mine) you'll have 2x^2 + 7x -4:: Infact:: we need 2x^2 - 7x -4 -- Exapnd the second one(Momma's) you'll have 2x^2 - 7x -4.

I didn't realise this point I was a bit rushy.

Sorry about that Momma, I'll be more focused next time.
 
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