# Thread: need help plz, factoring

1. ## need help plz, factoring

i have two problems like this

6y^2+y-15

but whenever i try to factor it i always get prime so could you guys just like give me an example or something similar to that problem because i cant find anything about that in my notes thank you

2. Originally Posted by elfen_lied
i have two problems like this

6y^2+y-15

but whenever i try to factor it i always get prime so could you guys just like give me an example or something similar to that problem because i cant find anything about that in my notes thank you
(2*y - 3)*(3*y + 5)

3. Originally Posted by AfterShock
(2*y - 3)*(3*y + 5)
uh.....whats that?????

4. Originally Posted by elfen_lied
uh.....whats that?????
You asked how to factor 6*y^2+y-15, which is:

(2*y - 3)*(3*y + 5)

If you expand it by using FOIL, you will see it is 6*y^2+y-15:

[(2y*3y) + (2y*5) + (-3*3y) + (-3*5)] = 6y^2 + 10 y - 9y -15 = 6y^2 + y - 15

5. Originally Posted by AfterShock
You asked how to factor 6*y^2+y-15, which is:

(2*y - 3)*(3*y + 5)

If you expand it by using FOIL, you will see it is 6*y^2+y-15:

[(2y*3y) + (2y*5) + (-3*3y) + (-3*5)] = 6y^2 + 10 y - 9y -15 = 6y^2 + y - 15

uh can u show me how you got it?

6. Originally Posted by elfen_lied
uh can u show me how you got it?
Intuition. At your level, you will want to do a lot of guessing and checking, as I explain below.

Well, Wikipedia can probably explain it better than I could. Take a look at:

Factorization - Wikipedia, the free encyclopedia

I can just look at the problem and immediately see that it factors to that. You want your middle and outer terms to equal y (in this case -9y + 10y) and you want to make sure you have degree 2 (y^2). Specifically, you want 6y^2, therefore will want the first terms of each composition to be either:

1, 6
6, 1
3, 2
2, 3

And finally you want the 2nd terms of each composition to equal -15; thus, this will help you determine which of the combinations above you need to factor the whole expression, since you want the 6y^2 and -y to be fixed.

It takes practice.