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anonymous

  • one year ago

Solve x2 + 8x − 3 = 0 using the completing-the-square method. A.x = four plus or minus the square root of three B.x = negative four plus or minus the square root of three C.x = four plus or minus the square root of nineteen D.x = negative four plus or minus the square root of nineteen

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  1. welshfella
    • one year ago
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    (x + 4)^2 - 16 - 3 = 0 can you see why i subtract 16 ?

  2. anonymous
    • one year ago
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    nope lol

  3. welshfella
    • one year ago
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    ok so to complete the square you first divide the coefficient of x in the original equation by 2 so here its +8 / 2 = +4 so we write (x + 4)^2 - thats the square bit but if you expand this it comes to x^2 + 8x + 16. So to make it equal to x^2 + 8x we have to subtract 16

  4. anonymous
    • one year ago
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    okay i dont undertand how there is a squaare root in the answer tho

  5. welshfella
    • one year ago
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    as an identity in general form its is x^2 + bx = (x + (b/2)^2 - ( b/2)^2

  6. welshfella
    • one year ago
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    because we have a square in the equation (x + 4)^2 -3 - 16 = 0 (x + 4)^2 = 19 taking square roots x + 4 = +/- sqrt 19

  7. welshfella
    • one year ago
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    x = -4 +/- sqrt 19

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