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6 January, 13:23

Use completing the square to solve for x in the equation (x-12) (x+4) = 9.

X = - 1 or 15

X = 1 or 7

X=41 141

x = 4 + 173

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Answers (1)
  1. 6 January, 14:23
    0
    x = 4 + sqrt (73) or x = 4 - sqrt (73)

    Step-by-step explanation by completing the square:

    Solve for x:

    (x - 12) (x + 4) = 9

    Expand out terms of the left hand side:

    x^2 - 8 x - 48 = 9

    Add 48 to both sides:

    x^2 - 8 x = 57

    Add 16 to both sides:

    x^2 - 8 x + 16 = 73

    Write the left hand side as a square:

    (x - 4) ^2 = 73

    Take the square root of both sides:

    x - 4 = sqrt (73) or x - 4 = - sqrt (73)

    Add 4 to both sides:

    x = 4 + sqrt (73) or x - 4 = - sqrt (73)

    Add 4 to both sides:

    Answer: x = 4 + sqrt (73) or x = 4 - sqrt (73)
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