Got a math sum I'm working on thats troubling me.

$\displaystyle {x}^{2} + 4x - 8$ can be written in the form $\displaystyle {(x + p)}^{2} + q $

Find the values of $\displaystyle p$ and $\displaystyle q$

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- May 6th 2011, 03:24 AMyorkeyFinding values of quadratic equation
Got a math sum I'm working on thats troubling me.

$\displaystyle {x}^{2} + 4x - 8$ can be written in the form $\displaystyle {(x + p)}^{2} + q $

Find the values of $\displaystyle p$ and $\displaystyle q$ - May 6th 2011, 03:27 AMmr fantastic
You have two options, both require that you have the necessary knowledge and understanding.

Option 1: Complete the square for x^2 + 4x - 8 and compare with (x + p)^2 + q.

Option 2: Expand (x + p)^2 + q and equate the coefficients of the various powers of x with the corresponding coefficients in x^2 + 4x - 8. - May 6th 2011, 03:41 AMyorkey
Ok great! Thanks

p = 2

q = -8

Does that work? - May 6th 2011, 03:59 AMDrSteve
$\displaystyle {(x + 2)}^{2} - 8= x^2+2x+2x+4-8= x^2+4x-4 $.

So p looks correct, but q does not. You almost got it though. - May 6th 2011, 04:07 AMyorkey
Oh I'm a retard. My reasoning went something like this:

(x + 2)^2 is expanded to x^2 + 4, which it obviously is NOT. So q is -12, right? - May 6th 2011, 05:19 AMmasters
- May 6th 2011, 05:28 AMyorkey
Y'all are legends, thanks.

/this case is closed