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Find the extremum of f(x,y) subject to the given constraint, and state whether it is a maximum or a minimum. f (x,y) =3x2+ y?-xy; x+y=20 Find the Lagrange function F(x,y,A.). F(x,y.A) = - A ( D Find the partial derivatives Fx. Fy, and Fx- E There is a value of located at (x, y) = (Type an integer or a fraction. Type an ordered pair, using integers or fractions.)