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der
Lv 4
der asked in Science & MathematicsMathematics · 1 decade ago

I need to use the square root property to solve this problem?

(c - 2)^2 = 12

c^2 + 8 = 12

Then I would subtract 8 from both sides

c^2 = - 4

Is this correct or not

Thanks

7 Answers

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  • ?
    Lv 7
    1 decade ago
    Favorite Answer

    not correct

    (c-2)^2 =c^2 -4c +4 =12

    c^2 -4c -8 =0

    solution

    (c - 2)^2 =12

    c-2 =sqrt(12) = 3.464

    c =3.464 +2 =5.464

  • 1 decade ago

    Doesn't seem quite right - as you've seen, you'd need c to be the square root of -4, which can be done, but then wouldn't solve the original equation.

    I would take the square root first:

    (c-2) = SqRoot(12)

    c = SqRoot(12)+2

    I think in your attempt you didn't square the bracket quite right:

    (c-2)^2 = (c-2)(c-2) = c^2 - 2c - 2c + 4 = c^2 - 4c + 4

    Set that equal to 12:

    c^2 - 4c + 4 = 12

    c^2 - 4c - 8 = 0

    Then use the quadratic formula to solve for c:

    c = [-(-4) +/- SqRoot ((-4)^2)-4*1*(-8)) ] / 2(1)

    c = [4 +/- SqRoot (16+32)] / 2 = [4 +/- SqRoot (48)] / 2 = 2 +/- SqRoot (12) as above.

    (Note in the first answer above I hadn't considered the negative root. Whether or not you need to depends on the level of maths you're at.

    Hope that helps.

    Source(s): No sites. But I have done a maths degree!
  • 1 decade ago

    Your expansion of (c-2)^2 is wrong . It should be c^2-4c+4.

    There is another way . Take the sqroot

    c-2=plus minus root of 12 .

    Root of 12 is 2 x root of 3..

    c= 2 plus/minus (2 multiplied by root of 3).

    You should get the same answer by solving c^2-4c-8=0.

  • Anonymous
    1 decade ago

    This is what you need to do:

    (1) (c - 2)^2 = 12

    Take the sqrt of both sides:

    => (c - 2) = +/- sqrt(12) = +/-sqrt(2*2*3) = +/- 2sqrt(3)

    Add 2 to both sides:

    => c = +/- 2 sqrt(3) + 2 or

    => c = [2 sqrt(3) - 2] or c = [2 + 2 sqrt(3)]

    (2) c^2 + 8 = 12

    => c^2 = 4

    => c = +/- sqrt(4)

    => c = 2 or - 2

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  • 1 decade ago

    not quite, (c-2)^2 means (c-2)*(c-2) then to simplify you'd use foil method to end up with c^2-4c+4 but in this question I think you would take square root of both sides to give you c-2=sqrt(12) then add 2 to both sides to end up with c=sqrt(12)+2

  • Ed I
    Lv 7
    1 decade ago

    It is not correct.

    c - 2 = ± 2√3

    c = 2 ± 2√3

  • 5 years ago

    (5k-a million)^2 = 25k^2 -10k + a million 25*ok^2 - 10k + a million - 23 = 25k^2 - 10*ok - 22 = 0 a=25 , b= -10 , c = -22 quadratic formula: (-b +/- sqrt(b^2-4ac)/2a the +/- is plus or minus! once you upload it provides you you with the first root and once you subtract it provides you you with the 2d root. wish this facilitates

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