III: (10 points) Score V: (10 points ) Score Find lim 10+1-1 xy Find the extreme values of f(x, y) =4(x-y)-x -y IV: (10 points ) Score Letx +y' +2' -3z=0, evaluate Score VI: (10 points) (1) (2) ax Find the general solution of the following differential equations. y' '- 3y +2y=(VII: (10 points) Score Score Find the total differential of the function = = xy + y. IX: (10 points) Sketch the graph, y = x in three-dimensional space. VIII: (10 points) Score Evaluate the following double integrals [fetty dady , where D is enclosed by the circle x' + y' =4 (polar coordinate)