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Michael Ward
science forum beginner
Joined: 30 Apr 2005
Posts: 22
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 Posted: Mon Jun 12, 2006 3:14 pm Post subject:
New Problem
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How do you factor 2m^2 - m - 7 = 0
The question is asking me to find the roots, and I assume you have to factor it out first. |
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Pubkeybreaker
science forum Guru
Joined: 24 Mar 2005
Posts: 333
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| Posted: Mon Jun 12, 2006 4:10 pm Post subject:
Re: New Problem
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Lisa wrote:
| Quote: | How do you factor 2m^2 - m - 7 = 0
The question is asking me to find the roots, and I assume you have to factor it out first.
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May I suggest that you show us what you have already done?
We are not here to do your homework for you.
Also, I thought this newsgroup was devoted to undergraduate level
math and not freshman high school level math???
I will give hints in socratic style:
(1) If one root is rational, what can you say about the other one?
(2) If m = a/b, for integers a and b, what can you say about a and
b
with respect to the coefficients of the polynomial?
(3) If the roots are not rational, then what method(s) are available to
solve it?
(4) What is the required condition on the discriminant for the roots to
be rational?
What is the value of the discriminant? |
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cody.roux@gmail.com
science forum beginner
Joined: 30 Apr 2006
Posts: 34
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| Posted: Mon Jun 12, 2006 4:47 pm Post subject:
Re: New Problem
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Lisa a écrit :
| Quote: | How do you factor 2m^2 - m - 7 = 0
The question is asking me to find the roots, and I assume you have to factor it out first.
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1) open a textbook
2) read it
3) apply the appropriate result to your problem
Thanks! ;)
Cody |
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Michael Ward
science forum beginner
Joined: 30 Apr 2005
Posts: 22
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| Posted: Mon Jun 12, 2006 5:20 pm Post subject:
Re: New Problem
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nothing I do works..(2x-7)(x+1) (2x+7) (x-1) nothing works what am I doing wrong? |
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Pubkeybreaker
science forum Guru
Joined: 24 Mar 2005
Posts: 333
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| Posted: Mon Jun 12, 2006 5:38 pm Post subject:
Re: New Problem
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Lisa wrote:
| Quote: | nothing I do works..(2x-7)(x+1) (2x+7) (x-1) nothing works what am I doing wrong?
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Perhaps the fault lies in the assumption that it can be factored??????? |
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Paul
science forum beginner
Joined: 13 Nov 2005
Posts: 18
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| Posted: Mon Jun 12, 2006 6:02 pm Post subject:
Re: New Problem
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| Quote: |
Lisa wrote:
How do you factor 2m^2 - m - 7 = 0
The question is asking me to find the roots, and I
assume you have to factor it out first.
May I suggest that you show us what you have already
done?
We are not here to do your homework for you.
Also, I thought this newsgroup was devoted to
undergraduate level
math and not freshman high school level math???
Perhaps this is college pre-algebra or algebra at a University; hence, by definition undergraduate. |
| Quote: | I will give hints in socratic style:
(1) If one root is rational, what can you say about
the other one?
(2) If m = a/b, for integers a and b, what can
you say about a and
b
with respect to the coefficients of the polynomial?
(3) If the roots are not rational, then what
method(s) are available to
solve it?
(4) What is the required condition on the
discriminant for the roots to
be rational?
What is the value of the discriminant?
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Paul
science forum beginner
Joined: 13 Nov 2005
Posts: 18
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| Posted: Mon Jun 12, 2006 6:04 pm Post subject:
Re: New Problem
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| Quote: |
Lisa a écrit :
How do you factor 2m^2 - m - 7 = 0
The question is asking me to find the roots, and I
assume you have to factor it out first.
1) open a textbook
2) read it
3) apply the appropriate result to your problem
Thanks! ;)
Cody
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Sarcasm is really unnecessary. |
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Paul
science forum beginner
Joined: 13 Nov 2005
Posts: 18
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| Posted: Mon Jun 12, 2006 6:06 pm Post subject:
Re: New Problem
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Try completing the square or the quadratic formula. You can use both to double check your self.
If you try either and are still unsure... post what you have done and someone (hopefully less sarcastic then previous posts) will show you your mistakes.
Paul |
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Dana DeLouis
science forum beginner
Joined: 06 Mar 2006
Posts: 37
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| Posted: Mon Jun 12, 2006 11:45 pm Post subject:
Re: New Problem
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| Quote: | The question is asking me to find the roots
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I think you are looking for the following...
http://mathworld.wolfram.com/QuadraticFormula.html
| Quote: | ...I assume you have to factor it out first?
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Some can be factored, but this one in particular doesn't seem to factor into
anything useful...as far as I can tell.
Good luck...
--
HTH. :>)
Dana
"Lisa" <mikeward1980@yahoo.com> wrote in message
news:20717893.1150125300808.JavaMail.jakarta@nitrogen.mathforum.org...
| Quote: | How do you factor 2m^2 - m - 7 = 0
The question is asking me to find the roots, and I assume you have to
factor it out first. |
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Bob
science forum Guru Wannabe
Joined: 13 Jan 2006
Posts: 115
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| Posted: Tue Jun 13, 2006 1:25 am Post subject:
Re: New Problem
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On Mon, 12 Jun 2006 11:14:30 EDT, Lisa <mikeward1980@yahoo.com> wrote:
| Quote: | How do you factor 2m^2 - m - 7 = 0
The question is asking me to find the roots, and I assume you have to factor it out first.
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If you have a quadratic equation and aren't sure how to approach it,
the best general way is to use the quadratic formula. If you can
easily find factors, fine, but spending much time looking for them is
not so good. Just go directly to the general method, the quadratic
equation.
bob |
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Paul
science forum beginner
Joined: 13 Nov 2005
Posts: 18
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| Posted: Tue Jun 13, 2006 2:56 am Post subject:
Re: New Problem
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| Quote: | How do you factor 2m^2 - m - 7 = 0
The question is asking me to find the roots, and I
assume you have to factor it out first.
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I'm getting tired of see everyone post ... so here it is.
Completing the square:
2x^2 - x - 7 = 0
Add 7 to both sides.
=> 2x^2 - x = 7
Multiply through by 1/2.
=> x^2 - (1/2)x = (7/2)
Complete the square by taking half the coefficient of x, square it and add it to both sides. We have,
((-1/2)/2)^2 = 1/16 and so
=> x^2 - (1/2)x + (1/16) = (7/2) + (1/16)
Simplify.
=> (x - (1/4))^2 = (57/16)
Square root both sides.
=> x - (1/4) = +- (sqrt(57)/4)
Add 1/4 to both side.
=> x = (1 +- sqrt(57))/4
The end.
Use quadratic formula to check my work. |
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David C. Ullrich
science forum Guru
Joined: 28 Apr 2005
Posts: 2250
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| Posted: Tue Jun 13, 2006 9:05 am Post subject:
Re: New Problem
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On Mon, 12 Jun 2006 11:14:30 EDT, Lisa <mikeward1980@yahoo.com> wrote:
| Quote: | How do you factor 2m^2 - m - 7 = 0
The question is asking me to find the roots, and I assume you have to factor it out first.
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Factoring is not the only way to find the roots... once you find the
roots you'll see why you couldn't factor it.
************************
David C. Ullrich |
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David C. Ullrich
science forum Guru
Joined: 28 Apr 2005
Posts: 2250
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| Posted: Tue Jun 13, 2006 9:09 am Post subject:
Re: New Problem
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On Mon, 12 Jun 2006 14:04:16 EDT, Paul <kryptos@verizon.net> wrote:
| Quote: |
Lisa a écrit :
How do you factor 2m^2 - m - 7 = 0
The question is asking me to find the roots, and I
assume you have to factor it out first.
1) open a textbook
2) read it
3) apply the appropriate result to your problem
Thanks! ;)
Cody
Sarcasm is really unnecessary.
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What sarcasm? What he wrote was excellent advice!
The OP has clearly just not learned one or two important
techniques that were covered in class - explaining to her
that she shouldn't expect to succeed in a math class if
she hasn't been bothering to learn the material is a
much more valuable bit of information than the solution
to this particular problem...
************************
David C. Ullrich |
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denver
science forum beginner
Joined: 28 Apr 2006
Posts: 10
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| Posted: Tue Jun 13, 2006 10:06 am Post subject:
Re: New Problem
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Lisa wrote:
| Quote: | How do you factor 2m^2 - m - 7 = 0
The question is asking me to find the roots, and I assume you have to factor it out first.
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I DONT SEE WHAT CAN BE THAT DIFFICULT IN THIS PROBLEM BECAUSE IT HAS
BEEN KNOW THAT IF IT DIFFICULT TO FACTOR AN EQUATION, YOU MUST USE THE
GENERAL FORMULAR( QUADRATIC FORMULAR) ax^2+bx+c, that all!! |
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tommy1729
science forum beginner
Joined: 23 Feb 2006
Posts: 33
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| Posted: Wed Jun 14, 2006 11:53 pm Post subject:
Re: New Problem
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yeah sounds more like old classic low level problem to me :p |
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