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 Algebra Pre-Algebra and Basic Algebra Math Forum

May 20th, 2015, 03:07 AM   #11
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Quote:
 Originally Posted by skipjack $\displaystyle \frac{x^2 - 121}{x^2 - 144} \cdot \frac{3x + 36}{2x + 22} = \frac{(x - 11)(x + 11)}{(x - 12)(x + 12)} \cdot \frac{3(x + 12)}{2(x + 11)} = \frac{3(x - 11)}{2(x - 12)}$
thanks what happens with the numbers 121 and 144, why do they disappear? May 20th, 2015, 07:27 PM #12 Senior Member   Joined: Nov 2010 From: Indonesia Posts: 2,001 Thanks: 132 Math Focus: Trigonometry It's because $\displaystyle x^2-a^2 = (x+a)(x-a)$, thus: $\displaystyle x^2-121 = x^2-11^2 = (x+11)(x-11)$ and $\displaystyle x^2-144 = x^2-12^2 = (x+12)(x-12)$ Tags letters, numbers, pull 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 bethewind Probability and Statistics 1 March 6th, 2015 03:19 PM xichyu Differential Equations 0 February 2nd, 2015 04:40 PM AzraaBux Calculus 4 July 19th, 2013 06:59 AM

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