# Thread: anyone know how to do this

1. ## anyone know how to do this

X^4 - 2x - 8 = 0

2. Originally Posted by inobd22
X^4 - 2x - 8 = 0
that's a hard one. it has no rational roots. and thinking up irrational roots is, well, pretty impossible. you probably have to use the "general formula" for solving quartic equations, which i can tell you is really complicated. check to see if you have a typo before looking it up

3. nope, no typo checked it like 10 times lol

4. Originally Posted by inobd22
nope, no typo checked it like 10 times lol
so yeah, like i said, there's no nice way to solve this. there are no rational roots. the roots are irrational, so you can't really come up with any (unless you're a super super genius). try looking up the general formula. did your professor mention that you would need it?

5. Originally Posted by Jhevon
so yeah, like i said, there's no nice way to solve this. there are no rational roots. the roots are irrational, so you can't really come up with any (unless you're a super super genius). try looking up the general formula. did your professor mention that you would need it?
let me follow up that question with this: Where did you get this question? Was it in a book? On a test? In a handout? Something your teacher wrote up on the board?

I can tell you with relative certainty this problem cannot be solved. To be specific, it CAN be solved if you plug it into a formula that is at least 10 pages long. Don't worry about finding the roots to this.

6. Originally Posted by ecMathGeek
let me follow up that question with this: Where did you get this question? Was it in a book? On a test? In a handout? Something your teacher wrote up on the board?

I can tell you with relative certainty this problem cannot be solved. To be specific, it CAN be solved if you plug it into a formula that is at least 10 pages long. Don't worry about finding the roots to this.
yeah, i actually tried doing this, (not completely by hand, i used a site to compute some parts), and i was getting complex numbers in intermediate steps, so i couldn't complete it. when i used a graphing utility to graph it, it showed two real roots, but i don't see how to get to them

7. Hmm, perhaps your teacher intended for you to practice calculator graphing. Perhaps a possibility, as my teacher has asked us to graph and find intersection points in the past for equations that require logs (that we haven't learnt yet).

8. Originally Posted by DivideBy0
Hmm, perhaps your teacher intended for you to practice calculator graphing. Perhaps a possibility, as my teacher has asked us to graph and find intersection points in the past for equations that require logs (that we haven't learnt yet).
that could be it. i definately know a graphing utility can handle it, i used one to plot the graph after all

9. Originally Posted by inobd22
X^4 - 2x - 8 = 0
I can understand your confusion over this polynomial equation but you were told (by me) in another post that this has to be done numerically. If you have a question about something I told you I'd appreciate it if you would ask in the same thread so that it's on topic.

The fact that this is the second time you posted this question AFTER I gave you a solution strikes me as being rather rude.

-Dan

10. sry topsquark... didnt think you would take it soo.....personal.. but anyway ya its a problem on a test.. i was absent for the test and he let me take it home ummm idk i guess monday ill go up to him and ask him after he grades it can he explain what he wanted for the problem because he didnt tell me anything special about it... "solve each polynomial equation" thats all the test says