Thursday, March 12, 2009

Question 7: Which method?

Out of the 4 methods of factorisation, state which method you would use for each of the two expressions. Explain your choice of method.

a) 4x²-12x+9

b) 4x²+4x-15
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2 comments:

  1. AnonymousMarch 12, 2009 at 11:52 PM

    Is a) 4x^2-12x+9 ?
    If it is, then my choice is using the formulae method because the equation can be easily solved by formulae 2 and my answer will be (2x-3)(2x-3).
    b) 4x^2+4x-15
    I will choose to use the cross-multiplication method because for the other three methods, there is no four factors in the equation for the grouping method, and there is no common factor among the equation, also for the formulae method, 15 cannot be square rooted, hence my choice is the cross-multiplication method whereby my answer
    is (2x+5)(2x-3)=0
    and my answer for x is -2.5 or x=1.5

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  2. AnonymousMarch 13, 2009 at 5:46 AM

    For a) I would use formulae method since it matches the a^2-2ab+b^2 formula.
    For B I would use cross-multiplication method as there is no common factor, only 3 terms and the expression does not match any of the formulae.

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