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    Hi,
    can someone tell me where I have gone wrong because I get a square root of negative 15, which is impossible.

    x2+8x-1=0
    x2+8x=1
    (x+4)2=-15
    x+4=square root of -15
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    (Original post by Louise_1988)
    Hi,
    can someone tell me where I have gone wrong because I get a square root of negative 15, which is impossible.

    x2+8x-1=0
    x2+8x=1
    (x+4)2=-15
    x+4=square root of -15

    x^2+8x-1=0
    (x+4)^2-17=0
    x+4 = +/- square root of 17
    x = - 4 +/- square root of 17.
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    (Original post by Louise_1988)
    Hi,
    can someone tell me where I have gone wrong because I get a square root of negative 15, which is impossible.

    x2+8x-1=0
    x2+8x=1
    (x+4)2=-15
    x+4=square root of -15
    x^2 + 8x - 1 = 0

    Completing the square: (x + 4)^2

    Multiplying this out: x^2 + 8x + 16 - you need to take away 17 to get -1

    => (x + 4)^2 - 17 = 0
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    (Original post by Louise_1988)
    Hi,
    can someone tell me where I have gone wrong because I get a square root of negative 15, which is impossible.

    x2+8x-1=0
    x2+8x=1
    (x+4)2=-15
    x+4=square root of -15
    you take 4^2 from the same side, so it becomes -16 - 1 = -17 then move it across.
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    (Original post by Louise_1988)
    Hi,
    can someone tell me where I have gone wrong because I get a square root of negative 15, which is impossible.

    x2+8x-1=0
    x2+8x=1
    (x+4)2=-15
    x+4=square root of -15
    technically root(-15) isnt impossible but thats a whole other story
 
 
 

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