September 9th, 2017, 06:31 PM  #1 
Senior Member Joined: Apr 2017 From: New York Posts: 162 Thanks: 6  Intermediate Value Theorem
question: Is there a number that is exactly 5 more than its cube? What I tried : x=number x+5=x^3 if we rearrange: x^3x5 after here I think I need to plug in two consequent numbers?(how do I pick that two numbers?) to see x^3x5<0 and x^3x5>0 and? 
September 9th, 2017, 06:33 PM  #2 
Senior Member Joined: Aug 2012 Posts: 2,409 Thanks: 753 
Try 0 and a trillion. How'd I guess those? You can see that for x near 0, the 5 predominates. And for x large, the x^3 predominates. But even x = 2 works since 2^3  2 = 6. 
September 10th, 2017, 04:12 AM  #3  
Math Team Joined: Jan 2015 From: Alabama Posts: 3,264 Thanks: 902  Quote:
Quote:
How do you pick them? 0 is always an easy first choice, then "guess and check"!  
September 10th, 2017, 10:11 AM  #4 
Global Moderator Joined: Dec 2006 Posts: 21,026 Thanks: 2257  
September 10th, 2017, 12:14 PM  #5 
Member Joined: May 2017 From: Russia Posts: 34 Thanks: 5 
$\displaystyle x^3x5$ has a real root because of its odd degree.


Tags 
intermediate, theorem 
Thread Tools  
Display Modes  

Similar Threads  
Thread  Thread Starter  Forum  Replies  Last Post 
Intermediate Value Theorem  deadweight  Calculus  3  September 12th, 2015 03:47 AM 
Intermediate Value Theorem  jiasyuen  Calculus  3  January 5th, 2015 05:11 AM 
Intermediate value theorem  nubshat  Calculus  1  October 23rd, 2013 12:32 AM 
intermediate value theorem  chris123  Real Analysis  0  February 21st, 2013 05:44 PM 
Help with the Intermediate Value Theorem  Twoxsmart  Calculus  1  January 28th, 2009 09:55 PM 