## sandy2413 3 years ago the factor 3m^3+5m^2-12m-20 help me plezz i have one day to finsh last resort

1. cathyangs

Ok, well I would start out by looking at the coefficients. Those are: 3, 5, -12, and -20. Do any of those have any factors in common? :)

2. sandy2413

3 has -12in common and 5 has -20 in common

3. cathyangs

Yes, so if you group the ones that have something in common with each other together...

4. sandy2413

what im lost

5. cathyangs

If you group the monomials (3m^3 is one monomial) that have factors in common together...you're basically just grouping the 3-coefficient monomial with the -12 coefficient monomial, and the same for the 5 and -20 ones. Then you can divide out the factor that each group has in common.

6. sandy2413

so for 3and -12 the grouping would be -4 and the grouping for 5 and -20 is -4 right?

7. cathyangs

Yes! So if you use the "reverse distributive property" on each group?

8. sandy2413

reverse distributive property ?

9. cathyangs

If you apply the distributive property, but reverse it. Instead of multiplying everything in parenthesis by the same thing, you divide "out" a common factor.

10. sandy2413

so (3-20)4 like that

11. cathyangs

um...Not quite. Do you know what a factor is? The GCF, or Greatest Common Factor of two numbers is the largest number that both of those numbers can both be evenly divide by. To put it simply, here's an example: the GCF of 40 and 8 is 8, because both 40 and 8 are evenly divisible y 8, with no remainders. Now fiind the GCF for 3 and -12 and the numbers 5 and -20

12. sandy2413

3 and 5

13. cathyangs

That's right. And now, can you group the numbers, and divide out the GCF for each group?

14. sandy2413

so 3 in to 3 is one 3 in to 12 is 4 5 in to 5 is one 5 in to 20 is 4

15. cathyangs

Yes. Can you rewrite each group with parenthesis around the quotients? ( the 3 and 4 in the first group, for example)

16. sandy2413

(3/3)=1 (3/12)=4 (5/5)=1 (5/20)=4

17. cathyangs

XD ok, that's one way to write it. Here's more of what I was looking for: For the first group: 3m^3-12m is rewritten as 3 (m^3-4) Try the second group.

18. sandy2413

5m^2-20 5(m^2-4

19. sandy2413

so was that right

20. sandy2413

cathyangs u there

21. cathyangs

Sorry, just a family thing. That's right! (but remember to close the parenthesis) Now look back at the first one. What other factor do the two monomials inside the parenthesis have in common? (Big 'ol hint, it's a variable)

22. sandy2413

m

23. cathyangs

And you can pull that out of the parenthesis, right? :) So now, write the two groups added together (since they were two parts of the same equation in the beginning)

24. sandy2413

3(m^3-4)5(m^2-20)

25. sandy2413

like this

26. cathyangs

*added together. you need a plus sign in there...also, double check each of the "groups" You forgot the m in the first one, and -20 should be something else in the second one ;)