Can somebody help break this problem down for me using the quadratic formula? Thanks!

x^2+2x-2=0

I know the answer is x=-1 plusminus square root 3 (don't know how to write that on here)

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- May 24th 2010, 12:53 PMfetuslasvegasQuadratic Formula Problem
Can somebody help break this problem down for me using the quadratic formula? Thanks!

x^2+2x-2=0

I know the answer is x=-1 plusminus square root 3 (don't know how to write that on here) - May 24th 2010, 01:00 PMe^(i*pi)
For $\displaystyle ax^2+bx+c = 0$ then $\displaystyle x = \frac{-b \pm \sqrt{b^2-4ac}}{2a}$

If you compare your equation to $\displaystyle ax^2+bx+c=0$ then you'll see that $\displaystyle a=1$, $\displaystyle b=2$ and $\displaystyle c=-2$. The place most people split up is a sign error when calculating $\displaystyle b^2-4ac$ - May 24th 2010, 01:14 PMfetuslasvegas
- May 24th 2010, 01:20 PMharish21
$\displaystyle x = \frac{-2 \pm \sqrt{4+8}}{2}$

$\displaystyle x = \frac{-2 \pm \sqrt{12}}{2}$

$\displaystyle x = \frac{-2 \pm 2\sqrt{3}}{2}$

so,

$\displaystyle x = \frac{-2 + 2\sqrt{3}}{2} = {\sqrt{3} -1}$

OR

$\displaystyle x = \frac{-2 - 2\sqrt{3}}{2}= {-\sqrt{3} -1}$

Both values of x satisfy your equation - May 24th 2010, 01:26 PMfetuslasvegas
- May 24th 2010, 01:35 PMharish21
- May 24th 2010, 01:45 PMfetuslasvegas
- May 24th 2010, 01:54 PMpickslides
$\displaystyle -2+2\sqrt{3} = 2\times -1+2\times \sqrt{3}$

Now 2 is common to both terms so it can be factored out giving

$\displaystyle 2\times -1+2\times \sqrt{3} = 2(-1+\sqrt{3})$

If you cannot follow this please revise basic factorisation before asking additional questions. - May 24th 2010, 02:12 PMfetuslasvegas