solve non-linear system: x^(x + y) = y^(x - y), x^2 * y = 1

mladmint

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Jun 7, 2009
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Find all positive number in system equations

\(\displaystyle x^{x\, +\, y}\, =\, y^{x\, -\, y}\)

\(\displaystyle x^2 y\, =\, 1\)
 
The second equation tells us that y is the reciprocal of x^2.

Since 1 is it's own reciprocal, we find our first solution by inspection.

x = 1

y = 1

Substituting 1/x^2 for y in the first equation leads to the following.

x^(x^3 + 1) = (x^2)^(1 - x^3)

Equating exponents leads to the following.

3x^3 - 1 = 0

This has one Real solution, and it provides a second solution to the original system.

x = cuberoot(9)/3

y = cuberoot(9)
 
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