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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
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Re: Help me understand this step in an algebraic simplificat

Quote:
 Originally Posted by SamSeymour So my question is, how does 2x + 2(3600/x) simplify to x + 3600/x? Help appreciated!
It doesn't. And, it should be easy to convince yourself that it doesn't. If you ever doubt an equality, plug in some numbers!

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
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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.
Attached Files Lecture 03(1).pdf (94.6 KB, 1 views) Lecture 03(2).pdf (23.5 KB, 3 views) Tags algebraic, simplification, step, understand Thread Tools Show Printable Version Email this Page Display Modes Linear Mode Switch to Hybrid Mode Switch to Threaded Mode Similar Threads Thread Thread Starter Forum Replies Last Post conure Algebra 3 October 21st, 2013 11:33 AM dalo Math Software 1 March 17th, 2013 10:19 PM iamdaniel Academic Guidance 3 February 2nd, 2012 08:42 PM Weiler Differential Equations 1 January 31st, 2012 07:15 AM simrat_sandy Algebra 1 July 12th, 2008 09:47 AM

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