View Full Version : How to factorise this equation?
Christal24
Oct 2, 2009, 11:30 PM
I am stuck again! I can't factorise this to find stationary points!
y= x^3 + x^2 - 4x - 4
y'= 3x^2 +2x-4
how to factorize??
galactus
Oct 3, 2009, 05:44 AM
I assume you want to factor 3x^{2}+2x-4?
It does not factor. That is why you are having a rough time.
Use the quadratic formula.
To tell rather or not a quadratic will factor or not, check the discriminant. b^{2}-4ac
If it is a perfect square, then it will factor. We have 2^{2}-4(3)(-4)=52
52 is not a perfect square so it is not factorable.
Unknown008
Oct 3, 2009, 08:33 AM
You can however find the stationary points using the formula that galactus said. He didn't say it directly, but you should already know it:
x = \frac{-b \pm \sqrt{b^2-4ac}}{2a}
You'll have two values, where the stationary points are found.
Christal24
Oct 3, 2009, 08:14 PM
yeah I did that. It's all good now. Thanks ^_^