What does that even mean.. Factors of b ? 1, 2, 3, 4, 6, 12..... All negative.. Now factors of b that add to get a... None of them add to get a...

Bold'd is wrong. tell me, when does -1 * -12 = -12? Try again.

So its those numbers all positive and all negative ?

-2 + 3


I guess I'm confused when u say factor.. Factoring I'm familiar with is format like

(x-2)^2

(X-2)(x-2). Etc

This is a different kind of factoring ?


So we use x^2 + ax+ b and find b factor values that add to a.. And if b is negative it is all negative and positive factors.

Now what do I do once I have -2 and 3.


Am I retarded ? This stuff is supposed to be very easy...

This post was edited by fingerling on Jan 22 2014 12:00am

1) does -2 * 3 = -12?
2) yes that is factoring. x^2 - 4x + 4 factors into (x-2)(x-2). notice that the factors of 4 (-2*-2) add to get -4. so what does x^2 +x - 12 factor into?

( x^2 + x -12) = 0 can be solved by factoring

or by using quadratic formula

those would be the only 2 methods you need to worry about.

what's the problem, you don't know how to factor? don't know about quadratic formula? , didn't read other posts

fixed^^^

To restate what the other posters have said:

The domain is every possible value x can have that won't make that function "blow up in your face".

The only way for something to go wrong with that function would be if you evaulated (plugged in a value for x) the denominator and got 0

So the domain is all real numbers except where:

x^2 + x - 12 = 0

So you need to solve that for, and it will give you value(s) for x that will make the function blow up in your face.

You can use many methods to solve it, but I will factor it:


x^2 + x - 12 = 0

(x+4)*(x-3) = 0

x = -4, x = 3

So the domain of x is all real values EXCEPT x = -4 and x = 3

If you don't understand how we factored that quadratic, you need to review this material:

I thought you said factors of b that add to a... And a is 1...

8x+x-12 is what it equals.

And maybe this:

you're telling me that 4 - 3 is not equal to 1?

/edit: oh, when i said factors of -12, i assumed you knew they had to multiply to get -12

-1 + 12 = 11
1 + -12 = -11
2 + -6 = -4
-2 + 6 = 4
3 + -4 = -1
-3 + 4 = 1 ---> our magic answer

This post was edited by carteblanche on Jan 22 2014 12:18am