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Michael Ward
science forum beginner

Joined: 30 Apr 2005
Posts: 22

Posted: Mon Jun 12, 2006 3:14 pm    Post subject: New Problem

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.
Pubkeybreaker
science forum Guru

Joined: 24 Mar 2005
Posts: 333

Posted: Mon Jun 12, 2006 4:10 pm    Post subject: Re: New Problem

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.

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?
cody.roux@gmail.com
science forum beginner

Joined: 30 Apr 2006
Posts: 34

Posted: Mon Jun 12, 2006 4:47 pm    Post subject: Re: New Problem

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.

1) open a textbook

3) apply the appropriate result to your problem

Thanks! ;)

Cody
Michael Ward
science forum beginner

Joined: 30 Apr 2005
Posts: 22

 Posted: Mon Jun 12, 2006 5:20 pm    Post subject: Re: New Problem nothing I do works..(2x-7)(x+1) (2x+7) (x-1) nothing works what am I doing wrong?
Pubkeybreaker
science forum Guru

Joined: 24 Mar 2005
Posts: 333

Posted: Mon Jun 12, 2006 5:38 pm    Post subject: Re: New Problem

Lisa wrote:
 Quote: nothing I do works..(2x-7)(x+1) (2x+7) (x-1) nothing works what am I doing wrong?

Perhaps the fault lies in the assumption that it can be factored???????
Paul1136
science forum beginner

Joined: 13 Nov 2005
Posts: 18

Posted: Mon Jun 12, 2006 6:02 pm    Post subject: Re: New Problem

 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?
Paul1136
science forum beginner

Joined: 13 Nov 2005
Posts: 18

Posted: Mon Jun 12, 2006 6:04 pm    Post subject: Re: New Problem

 Quote: Lisa a Ã©crit : 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.
Paul1136
science forum beginner

Joined: 13 Nov 2005
Posts: 18

Posted: Mon Jun 12, 2006 6:06 pm    Post subject: Re: New Problem

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
Dana DeLouis
science forum beginner

Joined: 06 Mar 2006
Posts: 37

Posted: Mon Jun 12, 2006 11:45 pm    Post subject: Re: New Problem

 Quote: The question is asking me to find the roots

I think you are looking for the following...

 Quote: ...I assume you have to factor it out first?

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.
Bob111
science forum Guru Wannabe

Joined: 13 Jan 2006
Posts: 115

Posted: Tue Jun 13, 2006 1:25 am    Post subject: Re: New Problem

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.

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
Paul1136
science forum beginner

Joined: 13 Nov 2005
Posts: 18

Posted: Tue Jun 13, 2006 2:56 am    Post subject: Re: New Problem

 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.

I'm getting tired of see everyone post ... so here it is.

Completing the square:

2x^2 - x - 7 = 0

=> 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)

=> x = (1 +- sqrt(57))/4

The end.

Use quadratic formula to check my work.
David C. Ullrich
science forum Guru

Joined: 28 Apr 2005
Posts: 2250

Posted: Tue Jun 13, 2006 9:05 am    Post subject: Re: New Problem

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.

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
David C. Ullrich
science forum Guru

Joined: 28 Apr 2005
Posts: 2250

Posted: Tue Jun 13, 2006 9:09 am    Post subject: Re: New Problem

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.

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
denver
science forum beginner

Joined: 28 Apr 2006
Posts: 10

Posted: Tue Jun 13, 2006 10:06 am    Post subject: Re: New Problem

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.

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!!
tommy1729
science forum beginner

Joined: 23 Feb 2006
Posts: 33

 Posted: Wed Jun 14, 2006 11:53 pm    Post subject: Re: New Problem yeah sounds more like old classic low level problem to me :p

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