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D( x )
x = 0
x = 0
x = 0
x in (-oo:0) U (0:+oo)
6*x-(((12*y)/21)/x)-(x*((2*y)/7)) = 0
6*x+(-4/7)*x^-1*y+(-2/7)*x*y = 0
6*x-4/7*x^-1*y-2/7*x*y = 0
2*x*(3-2/7*x^-2*y-1/7*y) = 0
-2/7*x^-2*y = -(3-1/7*y) // : -2/7*y
x^-2 = 7/2*y^-1*(3-1/7*y)
-2 < 0
1/(x^2) = 7/2*y^-1*(3-1/7*y) // * x^2
1 = 7/2*x^2*y^-1*(3-1/7*y) // : 7/2*y^-1*(3-1/7*y)
2/7*y*(3-1/7*y)^-1 = x^2
x^2 = 2/7*y*(3-1/7*y)^-1 // ^ 1/2
abs(x) = (2/7)^(1/2)*y^(1/2)*(3-1/7*y)^(-1/2)
x = (2/7)^(1/2)*y^(1/2)*(3-1/7*y)^(-1/2) or x = -((2/7)^(1/2)*y^(1/2)*(3-1/7*y)^(-1/2))
2*x = 0
2*x = 0 // : 2
x = 0
x in { 0}
x in { (2/7)^(1/2)*y^(1/2)*(3-1/7*y)^(-1/2), -((2/7)^(1/2)*y^(1/2)*(3-1/7*y)^(-1/2)) }
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