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 November 21st, 2014, 10:34 AM #1 Newbie   Joined: Nov 2014 From: Cottingham Posts: 8 Thanks: 0 Math Focus: Surds! Fractions! With powers! Or equations with powers and a number I have knowledge of solving fractions without powers, e.g. (2x+2)/3+x/5=10. But for (2x(x+1))/2=20, I got to 2x^2+2x=40, what do I do next? November 21st, 2014, 11:51 AM   #2
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Quote:
 Originally Posted by alifeee I got to 2x^2+2x=40, what do I do next?
That's a classical second degree equation.

\displaystyle \begin{aligned} & 2x^2 + 2x -40 = 0 \\ & x^2 + x - 20 = 0 \Rightarrow ax^2 + bx + c \\ & x = {-b \pm \sqrt{b^2 - 4ac} \over 2a} \\ \end{aligned}

You can continue..  November 21st, 2014, 12:24 PM #3 Global Moderator   Joined: Oct 2008 From: London, Ontario, Canada - The Forest City Posts: 7,945 Thanks: 1136 Math Focus: Elementary mathematics and beyond $\displaystyle x^2+x-20=(x+5)(x-4)$ November 21st, 2014, 03:47 PM   #4
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Quote:
 Originally Posted by alifeee But for (2x(x+1))/2=20, I got to 2x^2+2x=40, what do I do next?
$\displaystyle \color{blue}{\dfrac{\not{2}x(x+1)}{\not{2}}=20\ \Longleftrightarrow\ x(x+1)=20 \\\;\\ \\\;\\ x\ \ and\ \ x+1\ \ can\ be,\ here,\ two\ consecutive\ integers. \\\;\\ 4\cdot5 = 20 \\\;\\ (-5)\cdot(-4)=20}$ Tags algebra, equations, find, fractions, number, powers 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 caters Number Theory 67 March 19th, 2014 04:32 PM aurguplu Algebra 12 March 19th, 2013 01:50 PM Dougy Number Theory 6 June 17th, 2012 07:00 PM Skyer Algebra 11 October 22nd, 2011 05:17 AM jsmith613 Algebra 2 December 28th, 2010 10:27 AM

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