All about flooble | fun stuff | Get a free chatterbox | Free JavaScript | Avatars    
perplexus dot info

Home > Just Math
A Reciprocal And Square Problem (Posted on 2007-07-10) Difficulty: 2 of 5
Find all real pairs (p, q) satisfying the following system of equations:
                      p - 1/p - q2 = 0

                      q/p + pq = 4

See The Solution Submitted by K Sengupta    
Rating: 3.5000 (2 votes)

Comments: ( Back to comment list | You must be logged in to post comments.)
Solution Sol | Comment 6 of 7 |
p-1/p=q²
q(p+1/p)=4
square the second eq, q²*(p+1/p)²=16
(p-1/p)*((p-1/p)²+4)=16
let p-1/p=x
x³+4x-16=0 => (x-2)*(x²+2x+8)=0
x²+2x+8=0 has no real roots as its discriminant is less than 0
x=2 is the only solution.
Solving p-1/p=2 yields p=(1(+/-)√2)
substitute these in eq(2) to get q=+√2 for p=(1+√2)
and q=-√2 for p=(1-√2)

Edited on July 10, 2007, 11:48 am
  Posted by Praneeth Yalavarthi on 2007-07-10 11:44:22

Please log in:
Login:
Password:
Remember me:
Sign up! | Forgot password


Search:
Search body:
Forums (0)
Newest Problems
Random Problem
FAQ | About This Site
Site Statistics
New Comments (24)
Unsolved Problems
Top Rated Problems
This month's top
Most Commented On

Chatterbox:
Copyright © 2002 - 2024 by Animus Pactum Consulting. All rights reserved. Privacy Information