## Shannon20150 2 years ago Factor 2x4 - 20x2 - 78. 2(x2- 3)(x2- 13) ***** 2(x2+ 3)(x2- 13) 2(x2- 3)(x2+ 13) I think is right ****

1. Shannon20150

help me @FibonacciChick666

2. FibonacciChick666

I would like you to please first try and check your answer before I try the problem. You are going to do this by using the FOIL method.

3. Shannon20150

I did that's y I asked if its right

4. FibonacciChick666

alrighty good, I'm working on it right now

5. Shannon20150

okay lol

6. FibonacciChick666

ok so only one of your answers is correct. let's go through the process together.

7. rosedewittbukater

First factor out the 2 to get 2(x^4-10x^2-39) Replace any x^2 value with the variable a, so x^4 becomes a^2 because x^2 squared is x^4. You just do this to take the place of any x^2 s to make it easier, if that makes sense. So 2(a^2-10a-39). Then you can do regular factoring. 3 and -13 multiply to become -39, and 3-13=10. So The equation would become \[2(a+13)(a-3)\] Then change the a's back into x^2. So the answer is \[2(x ^{2}+3)(x ^{2}-13)\] So the answer is the second one.

8. FibonacciChick666

So the first thing that we want to do is pull out any like terms. What does each term in the expression have in common?

9. Shannon20150

x2

10. Shannon20150

okay I need help again

11. FibonacciChick666

ok, does the term (-78) contain an \[x ^{2}\]

12. Shannon20150

idk

13. rosedewittbukater

You can check your work by multiplying the factors back together using either the box method or FOIL. \[2(x ^{4}-13x ^{2}+3x ^{2}-39)\]Combine like terms to get \[2(x ^{4}-10x ^{2}-39)\]Then distribute the 2 \[2x ^{4}-20x ^{2}-78\]You know your answer is correct if it is the same as the original equation.

14. Shannon20150

will u help me in another problem @rosedewittbukater

15. FibonacciChick666

let's try a different approach. can you divide -78 by x^2 without leaving a remainder?

16. Shannon20150

yes

17. rosedewittbukater

Sure

18. Shannon20150

19. FibonacciChick666

ok so what is -78 divided by x^2 ?

20. rosedewittbukater

Where did you post it

21. Shannon20150

is it -39

22. Shannon20150

on open questions

23. FibonacciChick666

-39 is -78 divided by only 2 but think about the other terms listed do they also divide by 2?

24. Shannon20150

idk

25. rosedewittbukater

She's trying to ask what number or value can be divided out of every single part of the equation. There's no x^2 in 78 so the only common number that all of the numbers can be divided by is 2.

26. FibonacciChick666

let's try a slightly simplified example if you have the equation: \[2x+2\] What number is common to both terms?