Tuesday, January 23, 2007

Factoring and simplifying rational expresssions

Woo boy. I'm learning this at home, on my own, and I am struggling. Every time I sit down at my textbook I want to throw it across the room. I'm looking at purplemath.com for another perspective on how to do this and it's helping but it's still slow going.

I am still struggling with taking an expression like:

x2 + 2x - 15

and factoring it. It's a lot of guess work and I get very irritated and frustrated with that.

(x-3)(x+5) <--- I know this because I have the answer. LOL

It is not intuitive for me to look at the expression above and come to these factor. I know it will just take practice, but right now that doesn't console me much. ;)

I want a simple formula that guides me in how to factor these, instead of trying to figure out what multiples of -15 are going to help me find +2. Bah! I know how to do it. I just don't like doing it.

I'm afraid that when asked to 'simplify' or 'factor' an expression or equation that I will not be sure what I'm being asked, and that I will do the wrong thing. I have to learn this in a way that leaves me comfortable and confident, like addition and subtraction.

1 comment:

punchberry said...

Start with the last number in the equation you are factoring, and make a list of the possible constants for the factored equation. In the example you gave, there are only two possibilities: 3 and 5, or 1 and 15.

Now look at the middle number (-2). How can you come up with it from combos of the list above. The only possibility is 3-5=-2.

That's the thought process. The rest is just formatting (writing the answer as a "factored" equation).