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Thread: factorise

  1. February 24th 2010, 09:34 PM #1
    Tessarina
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    Exclamation factorise

    please fully factorise:

    49-(x-4)^2
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  2. February 24th 2010, 09:47 PM #2
    drewbear
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    49-(x-4)^2

    <br /> 49-(x-4)(x-4)<br />

    <br /> 49-(x^2-8x+16)<br />

    <br /> 49-x^2+8x-16<br />

    <br /> -x^2+8x+33<br />

    <br /> (-x+11)(x+3)<br />
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  3. February 25th 2010, 01:27 AM #3
    HallsofIvy
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    But why in the world would you multiply something you want to factor?

    Tessarina, one of the easiest factoring formulas is the "difference of squares" formula: a^2- b^2= (a- b)(a+ b).

    Here, a^2= 49= 7^2 and (x-4)^2.

    49- (x-4)^2= (7- (x-4))(7+ (x-4))= (11- x)(3+ x).
    Last edited by mr fantastic; February 25th 2010 at 01:36 AM. Reason: Fixed math tag
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