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Take Second Degree, Solve For Real (Posted on 2007-04-27) Difficulty: 2 of 5
Determine all possible real pairs (m,n) satisfying the following system of equations:

mn2 = 15m2+ 17mn + 15n2

m2n = 20m2 + 3n2

  Submitted by K Sengupta    
Rating: 3.0000 (1 votes)
Solution: (Hide)
Multiplying the first equation by m and the second equation by n and subtracting the second result from the first we obtain:

15m^3 - 3*m^2*n + 15m*n^2 - 3*n^3 = 0
Or, 5m^3 - m^2*n + 5m*n^2- n^3 = 0
Or, (5m-n)(m^2 + n^2) = 0;

Now, if, m^2 + n^2 = 0 then m is imaginary whenever n is real and vice versa.This is a contradiction.

Accordingly, 5m = n, and substituting this in the second equation, we obtain:
5*m^3 = 95*m^2; so that :
Either, m = 0; giving n = 0
Or, m= 19; giving n = 95

Consequently, (m, n) = (0,0); (19, 95) are the only possible solutions to the given problem.

Comments: ( You must be logged in to post comments.)
  Subject Author Date
Questionre: SolutionBractals2007-04-27 20:10:32
SolutionSolutionhoodat2007-04-27 18:08:36
SolutionSolutionBractals2007-04-27 12:05:06
solutionxdog2007-04-27 10:59:26
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