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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
- ?Lv 71 decade agoFavorite 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
- MatthewLv 71 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! - Rajesh KochharLv 61 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.
- Anonymous1 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
- 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