Need some math help, Algebra II

[ViperMagic]

Ok, I have to do these problems by Completing the Square, heres where I'm stuck...

X^2+4X-8=0
X^2+4X=8
X^2+4X+4=12
(X+2)^2=12
X+2=[Square root]12
Now what do I do? I have no idea. Help!

 

[HombrePequeno]

Uh subtract 2 so you'd have -2+&- [square]12 ?

 

[ViperMagic]

Yeah, but dnot I have to do all that + crap? and then wouldnt I have to reduce all that? None of which I know how to do

 

[iamwiz82]

link

this one will solve it for you.

 

[fatalbert]

ummm,


your math is wrong


(X+4)^2 = X^2+8X+16

not X^2+4X+4

so try factoring again and then it might make more sense

 

[XZeroII]

<<
X^2+4X-8=0
X^2+4X=-8
X^2+4X+4=12
(X+4)^2=12
X+2=[Square root]12
>>



X^2+4X-8=0
X^2+4X=8
X^2+4x+4=12
(x + 2)^2 = 12
Sqrt(x + 2)^2) = Sqrt(12)
X + 2 = Sqrt(12)
X = Sqrt(12) - 2

Took me a couple tries, but I got it. Remind me to never figure this out on a computer again. Pen and paper are the way to go.

 

[HombrePequeno]

Don't you add 8 to the other side instead of subtracting it?

 

[ViperMagic]

ok, both errors are fixes, they were typos, not what I had written down

 

[GermyBoy]

Remember that you can turn root 12 into 2 * root 3. That way you can have 2 * (1 + root 3), which is good enough for any math teacher to jerk off to.