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anonymous

  • 5 years ago

solve the quadratic equation by completing square z^2 +16z + 47 =0 a. z=-8+/-sqrt17 b. z=8+sqrt17 c. z= -16 +sqrt47 d. z=8 +/- sqrt47

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  1. anonymous
    • 5 years ago
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    so z has a coefficient of 1

  2. anonymous
    • 5 years ago
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    so we dont have to worry about it

  3. anonymous
    • 5 years ago
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    i guess you prolly already know that a=1, b=16, and c=47

  4. anonymous
    • 5 years ago
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    but you get all the z's on one side, and the constants on the other, so you rearrange it so now the equation looks like this: z^2 + 16z = -47

  5. anonymous
    • 5 years ago
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    now take half of the b coefficient, so (16/2) and square it, so (16/2)^2 so 8^2 = 64

  6. anonymous
    • 5 years ago
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    add that to both sides of your new equation

  7. anonymous
    • 5 years ago
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    so now you got z^2 + 16z + 64 = -47 + 64

  8. anonymous
    • 5 years ago
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    now you can simplify that so its z^2 + 16z +64 = 17

  9. anonymous
    • 5 years ago
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    now FOIL that equation on the left side there...which is simply (z + 8) (z + 8)

  10. anonymous
    • 5 years ago
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    cuz that will make z^2 + 16z + 64 again

  11. anonymous
    • 5 years ago
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    so basically you have (z + 8) ^2 = 17

  12. anonymous
    • 5 years ago
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    so to get rid of the ^2 just take the square root of both sides

  13. anonymous
    • 5 years ago
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    now u got z + 8 = sq. root 17

  14. anonymous
    • 5 years ago
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    so then it would be -8=.- sqrt 17 is that right?

  15. anonymous
    • 5 years ago
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    right...i was just a bit confused by your choice of answers there, but obviously C and D are wrong and since you would subtract 8 to get z by itself then there has to be a -8 in the answer, so yeah A is the right answer...maybe i'm just confusing myself cuz its written on a computer and not on paper lol

  16. anonymous
    • 5 years ago
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    lol thanks a bunch

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