I have 2 questions on this assignment that I cant get done.

question 1 : 2x^3 + 3xy^2 - y^3 =0

Question 2: find the equation of the tangent to the curve xy^2 + 3x -3y=6. at the point (2,1)

After differentiation then do i set the function dy/dx to equal 0? and substitute for zero...find 2nd deriv then sub for 2 and 1?