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Three surfaces, one real point? (Posted on 2007-02-07) Difficulty: 3 of 5
Determine whether there exist real numbers x, y and z satisfying the following system of equations:

x²+4yz+2z = 0; x+2xy+2z² = 0; 2xz+y²+y+1 = 0

  Submitted by K Sengupta    
Rating: 5.0000 (1 votes)
Solution: (Hide)
By the problem:
(1)x^2 + 4yz+2z = 0;
(2) x+2xy+ 2z^2 = 0;
(3) 2xz+y^2+y+1 = 0

If x=0 then from (3), we obtain:
y^2+y+1 = 0; which does not contain any real solution and is thus a contradiction.

On the other hand, if z = 0, then from (1), we obtain:
x = 0, which is not feasible for obvious reasons.
Accordingly xz must be non-zero.

From (1) and (2), we obtain:
x^2 = -2z(2y+1) and 2z^2 = -x(2y+1); so that
2(x^2)(z^2) = 2xz(2y+1)^2
Or, xz = (2y+1)^2

Substituting this in (1), we obtain:
2(2y+1)^2 + y^2+y+1 = 0
Or, 3y^2 + 3y +1 = 0, which do not possess any real solution in y.
Consequently, no solution is possible for the given problem.

Comments: ( You must be logged in to post comments.)
  Subject Author Date
SolutionSolutionBractals2007-02-10 12:17:44
Solutionhoodat2007-02-07 22:24:15
SolutionSolutionTamTam2007-02-07 17:14:44
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