|x+3|+(y-1/2）^2=0|x+3|=0,(y-1/2）^2=0x=-3y=1/26x^2y+2xy-3x^2y^2-7x-5yx-4y^2x^2-6x^2y =6x^2y-6x^2y +2xy-5yx-3x^2y^2-4y^2x^2-7x=-3xy-7x^2y^2-7x=-3*(-3)*1/2-7*(-3)^2*(1/2)^2-7*(-3)=9/2-63/4+21=39/4