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Factorising problem

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AngloScot | 18:11 Fri 24th Dec 2004 | Science
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I am revising for the A-S Maths C1 paper in January. The answers in the textbook I am using apparently has some wrong answers, so I just need some help with the following 2 questions: Factorise

  1. 5x(squared)-10x = 4x+3
  2. (2x-5)(squared) = 7

Am I right in thinking that neither of these factorise?

Merry Christmas! 

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1.

1.  5x^2 - 10x = 4x + 3   move all terms to left hand side

    5x^2 - 14x - 3 = 0  which factorises to

    (5x + 1)(x - 3) = 0 

2.  (2x-5)^2 = 7

   4x^2 - 20x + 25 = 7  expanding lhs

  4x^2 - 20x + 18 = 0 which simplifies to

  2x^2 - 10x + 9 = 0, which I don't think factorises with integers.  The solutions to this second one are x = 0.5x(5 + or - sqrt(7))

Hope the C1 exam goes well - time for at least a 24 hour break in revising, I think.

Question Author

Lol yeah cheers Gnu, I did make a silly mistake on the first one, a good example of why I should have a break when revising! I'm glad the second one doesn't factorise though I will manage to sleep now!

s'called a graphical calculator

Trouble is with graphical calculators is you forget how to factorise, go off to uni where they aren't allowed (they weren't on my physics degree) and have to remember how to do it properly again!
Question Author
No calculators are allowed on the C1 paper.

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