/
CTK Exchange
Front Page
Movie shortcuts
Personal info
Awards
Reciprocal links
Privacy Policy

Interactive Activities

Cut The Knot!
MSET99 Talk
Games & Puzzles
Arithmetic/Algebra
Geometry
Probability
Eye Opener
Analog Gadgets
Inventor's Paradox
Did you know?...
Proofs
Math as Language
Things Impossible
My Logo
Math Poll
Other Math sit's
Guest book
News sit's

Manifesto: what CTK is about |Store| Search CTK Buying a book is a commitment to learning Table of content Things you can find on CTK Chronology of updates Email to Cut The Knot

CTK Exchange

Subject: "simple calculus or not?"     Previous Topic | Next Topic
Printer-friendly copy     Email this topic to a friend    
Conferences The CTK Exchange Middle school Topic #55
Reading Topic #55
Dejan
guest
Jan-08-02, 08:35 PM (EST)
 
"simple calculus or not?"
 
   Hi there,

It was a long time ago since I have been doing calculations like this one and I forgot most of it. I am not sure does this question fit here, but here it is:

Is it possible to find value for “X” from this?


26 = {X – (26 +X)/5}square + {10 – (26 +X)/5}square + {7 - (26 +X)/5}square + {4 - (26 +X)/5}square + {5 - (26 +X)/5}square

I know that "X" = 4 but could you please show all workings?

Thanks
Dejan


  Alert | IP Printer-friendly page | Edit | Reply | Reply With Quote | Top

  Subject     Author     Message Date     ID  
  RE: simple calculus or not? alexb Jan-08-02 1
     RE: simple calculus or not? Ian Jan-13-02 2
         RE: simple calculus or not? Laocon Jan-14-02 4
  RE: simple calculus or not? Dude Jan-13-02 3
  RE: simple calculus or not? Gunes Jan-14-02 5
     RE: simple calculus or not? Gunes Jan-14-02 6

Conferences | Forums | Topics | Previous Topic | Next Topic
alexb
Charter Member
672 posts
Jan-08-02, 08:38 PM (EST)
Click to EMail alexb Click to send private message to alexb Click to view user profileClick to add this user to your buddy list  
1. "RE: simple calculus or not?"
In response to message #0
 
   Why do you care about such a boring problem? Why do you think anybody would waste his time showing you all the workings?


  Alert | IP Printer-friendly page | Edit | Reply | Reply With Quote | Top
Ian
Charter Member
7 posts
Jan-13-02, 10:49 AM (EST)
Click to EMail Ian Click to send private message to Ian Click to view user profileClick to add this user to your buddy list  
2. "RE: simple calculus or not?"
In response to message #1
 
   If you are so interested in this problem, why not ask for advice on where to start in trying to solve the problem? this would probably be more productive. Try multiplying the brackets, and making it'say "X=...."


  Alert | IP Printer-friendly page | Edit | Reply | Reply With Quote | Top
Laocon
guest
Jan-14-02, 07:54 AM (EST)
 
4. "RE: simple calculus or not?"
In response to message #2
 
   Further...

Multiply out the brackets and group all similar terms (eg powers of x) together. Then you will need to find the order of the equation and use the best method to resolve the problem.

EG Quadratic (order 2) can be best solved using inspection (by simplifying the equation into (x-a)(x-b) = 0) or the formula:

x equals minus b plus or minus the square-root of (b squared minus 4 lots of a by c), all over twice a.

You could also try graphing the function,after simplifying to F(x) = 0 to find when it crosses the x-axis... yadda yadda yadda....


  Alert | IP Printer-friendly page | Edit | Reply | Reply With Quote | Top
Dude
guest
Jan-13-02, 07:54 AM (EST)
 
3. "RE: simple calculus or not?"
In response to message #0
 
   Your original problem

26 = {X – (26 +X)/5}square + {10 – (26 +X)/5}square + {7 - (26 +X)/5}square + {4 - (26 +X)/5}square + {5 - (26 +X)/5}square

can be rewritten as
26*25=(4*x-26)^2+(24-x)^2+(9-x)^2+(x+6)^2+(x+1)^2

The right hand side can be expanded and we find
that x must satisfy the equation
650=20*x^2-260*x+1370

Bringing the 650 to the other side and dividing by 20 gives us
x^2-13*x+36=0
factoring this we get
(x-4)*(x-9)=0

This shows us that the original problem has 2 solutions
x=4 and x=9.



  Alert | IP Printer-friendly page | Edit | Reply | Reply With Quote | Top
Gunes
guest
Jan-14-02, 03:00 PM (EST)
 
5. "RE: simple calculus or not?"
In response to message #0
 
   hmm, i am trying to understand what is supposed to be interesting about this problem. clearly you have a sort of distance equation in 5-dimensional euclidean space, and you have many 5's or relations to 5 (square(5)+1=26, square(5)-1=4). you also have that one of the points would be the diagonal of a 5-dimensional hypercube. but some of the numbers seem totally arbitrary in the '5' context' ...
perhaps, you are not merely trying to refresh your memory of highschol algebraic manipulations, but are rather trying to find a geometric short cut to this problem?


  Alert | IP Printer-friendly page | Edit | Reply | Reply With Quote | Top
Gunes
Member since Jan-14-02
Jan-14-02, 03:51 PM (EST)
Click to EMail Gunes Click to send private message to Gunes Click to view user profileClick to add this user to your buddy list  
6. "RE: simple calculus or not?"
In response to message #5
 
   oops, sorry... in my haste i made some dumb errors... of course i meant '5-1=4' not 'square(5)-1=4', and i meant 'the point on a 5-dimensional hypercube at the end of the diagonal from the origin' not 'the diagonal of a 5-dimensional hypercube'...

------------------------------------------------------------

"One must still have chaos in oneself to be able to give birth to a
dancing star."
-- Friedrich Neit'sche


  Alert | IP Printer-friendly page | Edit | Reply | Reply With Quote | Top

Conferences | Forums | Topics | Previous Topic | Next Topic

You may be curious to visit the old CTK Exchange archive.

|Front page| |Contents|

Copyright © 1996-2018 Alexander Bogomolny

[an error occurred while processing this directive]
 Advertise

New Books
Second editions of J. Conway's classic On Numbers And Games and the inimitable Winning Ways for Your Mathematical Plays