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February 4th, 2014, 11:29 AM  #1 
Newbie Joined: Feb 2014 Posts: 16 Thanks: 2  Help me understand this step in an algebraic simplification?
I am using a book to brush up on some math, and there is a step in a problem that I do not understand. I have a problem where I need to express the length of some rectangular fencing, P, as a function of one of the sides. If the sides are x and y, then the length of the fencing, P = 2x + 2y. I am given the area within the fence as 3600 sq. meters. Therefore, it is clear that xy = 3600 and y = 3600/x. So, to express the length of the fencing P as a function of x, I should plug this value for y into the original equation for P, which is P = 2x + 2y. This is 2x + 2(3600/x). All of these steps I can see on my own. However, the book has the answer as P = 2x + 2y = x + 3600/x. So my question is, how does 2x + 2(3600/x) simplify to x + 3600/x? Help appreciated! 
February 4th, 2014, 11:51 AM  #2 
Newbie Joined: Jan 2014 Posts: 10 Thanks: 0  Re: Help me understand this step in an algebraic simplificat
What you have there is right, P = 2x + 2(3600/x)... Is there any other information it gives you. Can you to reference the book? The book sounds a little iffy 
February 4th, 2014, 12:06 PM  #3  
Senior Member Joined: Jun 2013 From: London, England Posts: 1,316 Thanks: 116  Re: Help me understand this step in an algebraic simplificat Quote:
Try x = 1: 2x + 2(3600/x) = 2 + 7200 = 7202 x + 3600/x = 1 + 3600 = 3601 In fact 2x + 2(3600/x) = 2(x + 3600/x)  
February 4th, 2014, 12:49 PM  #4 
Newbie Joined: Feb 2014 Posts: 16 Thanks: 2  Re: Help me understand this step in an algebraic simplificat
Ha! Well thank you then. I should have thought to plug in some numbers, but I will next time! It is not a real book, but rather a written lecture from the math department of a university. Here are the two pages with this problem attached. 

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