Question 1196714
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find parametric equations for the line tangent to the curve of intersection 
of the given surfaces at the point (2,1,3)
x^4+6x^2y^2+y^4+2z^2=5, 
x^2-2y^2+4z^2=4
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Hello,  your  " problem "  is  FATALLY  WRONG,  because the point  (2,1,3)  belongs  NEITHER  of the two surfaces.


Indeed,  point (2,1,3)  is not a solution to given equations.