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July 24th, 2009, 04:55 PM  #1 
Member Joined: May 2009 Posts: 37 Thanks: 0  help with problem
the problem is this solve this problem by completing the square Code: 2x^212x+11 they (the book) says the answer is 2(x3)^27 could anyone offer a quick step by step so i can see where I am wrong or where they are wrong? thanks 
July 24th, 2009, 05:58 PM  #2 
Senior Member Joined: Apr 2007 Posts: 2,140 Thanks: 0  Re: help with problem
Expand algebraically, then this obviously tells you the reason.

July 24th, 2009, 06:04 PM  #3 
Member Joined: May 2009 Posts: 37 Thanks: 0  Re: help with problem
ya, no duh, but if i don't know the answer, how do i find it? what I am saying is this, I move the 11 over to the other side complete the square and end up with 2(x3)^2 = 11 then i move the 11 back over and have 2(x3)^2 + 11 and if i expand the problem then I have 2(x^2 6x +9) + 11 which then becomes 2x^2 12x +18 + 11 which becomes 2x^2  12x + 29 good luck factoring that am I saying 2x^2  12x +36  7 ??? i am getting lost here

July 24th, 2009, 06:07 PM  #4 
Senior Member Joined: Apr 2007 Posts: 2,140 Thanks: 0  Re: help with problem
Be smart. Do what I tell you, and you will logically understand the meaning of my words.

July 24th, 2009, 06:12 PM  #5 
Senior Member Joined: Apr 2007 Posts: 2,140 Thanks: 0  Re: help with problem
Sigh. Expanding the thing will become , and this is what you've got for part of your answer, which was wrong. But, this obviously tells you how to solve it now. 
July 24th, 2009, 06:13 PM  #6 
Member Joined: May 2009 Posts: 37 Thanks: 0  Re: help with problem
I did that before I posted the question...

July 24th, 2009, 06:14 PM  #7 
Senior Member Joined: Apr 2007 Posts: 2,140 Thanks: 0  Re: help with problem
I hope they've taught you subtraction back in the school days.

July 24th, 2009, 06:15 PM  #8 
Member Joined: May 2009 Posts: 37 Thanks: 0  Re: help with problem
if i am not given the answer, how do i work it forwards............

July 24th, 2009, 06:20 PM  #9  
Senior Member Joined: Apr 2007 Posts: 2,140 Thanks: 0  Re: help with problem Quote:
The problem asks to CTS in order to find the values for when the equation equals to . Let , where is our value we are looking for. Expand the expression, and we will get . , so the will tell ya what you need. , and so on.  
July 24th, 2009, 06:26 PM  #10 
Member Joined: May 2009 Posts: 37 Thanks: 0  Re: help with problem
that does make sense to me but my big problem is that, the answer is not a given, so you do not know that it will be  7 at the end, and I realized how to get the answer once i had the answer, but, is there always going to be a ( + k at the end of a factor problem? how would i choose it to be 7 if i do not know that it is supposed to be 7?


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