Find all positive number in system equations x^{x\, +\, y}\, =\, y^{x\, -\, y} x^2 y\, =\, 1
M mladmint New member Joined Jun 7, 2009 Messages 1 Jun 7, 2009 #1 Find all positive number in system equations \(\displaystyle x^{x\, +\, y}\, =\, y^{x\, -\, y}\) \(\displaystyle x^2 y\, =\, 1\)
Find all positive number in system equations \(\displaystyle x^{x\, +\, y}\, =\, y^{x\, -\, y}\) \(\displaystyle x^2 y\, =\, 1\)
mmm4444bot Super Moderator Joined Oct 6, 2005 Messages 10,962 Jun 8, 2009 #2 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)
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)