1.由均衡点条件“dy/dx= -20/y”可知,X的数量为20,Px·Qx+Py·Qy=270,可解得Qy=46,Qx=202.先对X求导,得 18-4X-Y=0 再对Y求导,得 15-Y-X=0两式联立,得X=1,Y=14,TU=1143.由条件可知,20X1+30X2=540U对X1求导得3X22 U对X2求导得6X1X23X22 /6X1X2=P1/P2所以,X1=3/4X2,代入,可得,X1=9,X2=12,U=3888