a Proton in a magnetic field follows a path on a coordinate grid modeled by the function f(x)=x^4-2x^2-15. What are the x-coordinates of the points on the grid where the proton crosses the x-axis?

Question

dape · Answer

Have you started working on the problem, do you know what equation you need to solve?

anonymous · Answer

no, i am completely lost. :/ sorry

dape · Answer

If you draw a pair of coordinate axes, you can see what value the function must be when it crosses the x-axis.

anonymous · Answer

ok. thanks!

dape · Answer

|dw:1378421284583:dw|

dape · Answer

From this figure you see that whenever f(x) crosses the x-axis it has the value 0.

dape · Answer

So the equation you need to solve to find for which x's the function crosses the x-axis is simply:
$$f(x)=0=x^4-2x^2-15$$

dape · Answer

Do you think you know how to solve that equation?

anonymous · Answer

Kind of...

anonymous · Answer

i can solve it now

dape · Answer

Great, let me know if you want me to check your answer when you got it.

anonymous · Answer

i'll be fine! thanks!

dape · Answer

Yeah, that's what I thought ;)

anonymous · Answer

haha thank you!