× Didn't find what you were looking for? Ask a question
Top Posters
Since Sunday
d
4
N
3
3
R
3
k
3
o
3
Z
3
j
3
s
3
d
3
J
3
1
3
Home Q & A Board Science-Related Homework Help Mathematics
New Topic  
smlyslvmel@aol. smlyslvmel@aol.
wrote...
Posts: 4
Rep: 0 0
11 years ago
Show that the equation x^3 -5x +7 can be rearranged as x = cuberoot(ax+b) where a and b are constants whose values are to be stated. Use the associated iterative formula, starting with x = -2.7 to state a root of x^3-5x+7=0 correct to 2 decimal places. Show using the sign-change method that this is indeed to the required accuracy.
Read 246 times
2 Replies

Related Topics

Replies
wrote...
#1
11 years ago
x^3 -5x +7 can be rearranged
  as x = cuberoot(ax+b)
wrote...
#2
11 years ago
Your first "equation" is an exprssion, so I assume you mean

x^3 -5x +7= 0

If so, then just add (5x - 7) to both sides to get x^3 by itself:

x^3 = 5x - 7

And then take the cube root of both sides.  My calculation converges to -2.74734654030721 after 22 iterations, but is equal to -2.75, to two decimal places, from the second iteration on.  I can't help you with the "sign change method".  I don't see any change in sign in the differences from term to term, and the terms are all negative, so I can't see what is changing sign.
New Topic      
Quick Reply
Explore
Post your homework questions and get free online help from our incredible volunteers
  1537 People Browsing
Start New Topic Take the Tour CoursesNew Study Tools Topics Trending Browse by Textbook
Live Chat
Related Images
  
 78
  
 393
  
 308
Your Opinion
What's your favorite funny biology word?
Votes: 401
Previous poll results: How often do you eat-out per week?