Got Homework?
Connect with other students for help. It's a free community.
Here's the question you clicked on:
 0 viewing
f(x) = x^3 + 8x  19
Show that the equation f(x)=0 has only one real root.
 one year ago
 one year ago
f(x) = x^3 + 8x  19 Show that the equation f(x)=0 has only one real root.
 one year ago
 one year ago

This Question is Closed

SpacelimbusBest ResponseYou've already chosen the best response.0
I can only recommend the NewtonMethod or the Method of Bisection for this problem.
 one year ago

ZeHanzBest ResponseYou've already chosen the best response.1
It is a polynomial of the 3rd degree. Look at the endbehaviour of the function: The limit of f(x) if x => infinity is also infinity. The limit of f(x) if x => infinity is also infinity. f is continuous for every x, so it must be 0 at least one time. Now look at the derivative: f'(x)=3x²+8. What do you know about the possible values of f' ?
 one year ago

alrightatmathsBest ResponseYou've already chosen the best response.0
Yeah, you know it has to have one because there is a change in sign basically. And are you saying that f'(x) will never be zero so there's no turning point?
 one year ago

alrightatmathsBest ResponseYou've already chosen the best response.0
Or that it's always positive.
 one year ago

ZeHanzBest ResponseYou've already chosen the best response.1
That is just what I wanted to say ;) So f is always increasing...
 one year ago
See more questions >>>
Your question is ready. Sign up for free to start getting answers.
spraguer
(Moderator)
5
→ View Detailed Profile
is replying to Can someone tell me what button the professor is hitting...
23
 Teamwork 19 Teammate
 Problem Solving 19 Hero
 Engagement 19 Mad Hatter
 You have blocked this person.
 ✔ You're a fan Checking fan status...
Thanks for being so helpful in mathematics. If you are getting quality help, make sure you spread the word about OpenStudy.