Factoring Trinomials (when normal method doesn't seem to be possible)

[Wikitiki]

Still working on that Algebra I review packet, hi again.

So I've been refreshing my memory on factoring trinomials- I get the "normal" method- Something like x²+4x+3 would factor out to (x+1)(x+3) because 1 * 3 = 3 and 1 + 3 = 4.

But I also have problems like: x²-x+2; 2 + -1 = 1, but 2 * -1 = -2. So it doesn't factor out evenly. I guess you could multiply the trinomial by -1, but I don't know how to go about factoring that.

And then there are problems like 7x²-31x-20. The only explanation I've seen regarding how to do this problem involved dividing out the 7 (or whatever number is in front of x²), which is not possible to do evenly as far as I know. So I basically have no idea where to start with this one.

 

[Deleted member 4993]

Still working on that Algebra I review packet, hi again.

So I've been refreshing my memory on factoring trinomials- I get the "normal" method- Something like x²+4x+3 would factor out to (x+1)(x+3) because 1 * 3 = 3 and 1 + 3 = 4.

But I also have problems like: x²-x+2; 2 + -1 = 1, but 2 * -1 = -2. So it doesn't factor out evenly. I guess you could multiply the trinomial by -1, but I don't know how to go about factoring that.

And then there are problems like 7x²-31x-20. The only explanation I've seen regarding how to do this problem involved dividing out the 7 (or whatever number is in front of x²), which is not possible to do evenly as far as I know. So I basically have no idea where to start with this one.

For those types of trinomials [not easily factorable (? factorized - factorizable - Jeff, Mark,???? help with symantics)] you need to use "quadratic formula". For quick over-view go to:

http://search.freefind.com/find.html?id=5014414&pageid=r&mode=ALL&n=0&query=factoring+quadratic

 

[Wikitiki]

(Sorry for taking so long to respond!)

I'm a bit confused (and I'm not sure how to word this). So the trinomial ax² + bx + c is exactly the same as the quadratic equation ax² + bx + c = 0? Is the '=0' understood?

In any event, is there a way to do these without using the quadratic formula? In the section after the one I'm working on the instructions explicitly say to use the quadratic formula, so I'm assuming that it shouldn't (or doesn't have to be) used with the problems in this one.