z=(x2y,xy2)求二阶偏导数,就是x二阶导,y二阶导,还有x再导y的

z=(x2y,xy2)求二阶偏导数,就是x二阶导,y二阶导,还有x再导y的 x3+x2y-xy2-y3= 3x2y+xy2-[2xy2-4x2y+(x2y-2xy2)] (4xy2-2x2y)-( )=x3-2x2y+4xy2+y3． 先化简在求值,5xyz-{2x2y-[3xyz-(4xy2-x2y)]}其中x=-2,y=-1,z=3 当x=-2,y=-1,z=3时,求3yz-{2x2y-[3xyz-﹙2xy2-x2y﹚]}的值 (x2y)3 × (-xy2)3 解方程组 x3+y3=468 x2y+xy2=420 （-1/2x2y）`（-3xy2）= 分解因式:X3+2X2Y+2XY2+Y3= 5xy2-【3xy2-(4xy2-2x2y)】+2x2y】+2x2y-xy2 化简,再求值 （3x2y-2xy2）-（xy2-2x2y）,其中x=-1,y=2． 当x=-2,y=1时,x2y-(2xy2+x2y)+(2xy2+4x3y)的值为 若m=x3-3x2y+2xy2+3y2 n=x3-2x2y+xy2-5y3,则2x3-7x2y+5xy2+14y2等于( )若m=x3-3x2y+2xy2+3y2 n=x3-2x2y+xy2-5y3,则2x3-7x2y+5xy2+14y2等于( )空里用字母表示 C3x2y-2xy2)-(xy2-2x2y),其中x=-1,y=2 化简：5（3x2y-xy2) * (xy2+3x2y) -3x2y+2x2y+3xy2-2xy2 已知:(x+2)2+|y+1|=0,求5xy2-{2x2y-[3xy2-(4xy2-2x2y)]}的值