设函数[tex=3.714x1.286]0pJOHBkNco2pBdZcb4O/fw==[/tex]，[tex=3.643x1.286]SipN0lNOORM7sQWOllYS9g==[/tex]的各个偏导数都存在且连续，证明：（1）[tex=5.286x1.357]ltDARfs76z/kxifRUr6UHSxJtp1d7LuZLloigAwIQCs=[/tex]（其中[tex=0.5x0.786]hycNLgozeED/VkKdun7zdA==[/tex]为常数）；（2）[tex=8.643x1.357]zrvesMESsUjRqUqP+9AadW3CYT//ag9Lxw0zrhBRlvmO6M/94KEZHR2nu4CYYlf6[/tex]；（3）[tex=8.5x1.357]VmsXBm+u7c99PHQ6sxJ6L9FE3WdLKqpgafBBPJs3amcdFFiknJUiMqO4c+NYbogE[/tex]；（4）[tex=8.929x2.429]YOlFNctOOqKjfYPmH1aJtmm+ciz8xxV1A+yxadshWFTXLXnxA5QTWGlISERrKgJFEZ0gPc+NkfpKnZqR5QT/gz7o8h2tT/ppTsAqBJdGXOw=[/tex]。