解答题   求u=xyzex+y+z的全微分.
 
【正确答案】
【答案解析】[解] 因u'x=(1+x)yzex+y+z,u'y=(1+y)xzex+y+z,u'z=(1+z)xyex+y+z
   故du=ex+y+z[(1+x)yzdx+(1+y)xzdy+(1+z)xydz].