• 2022-06-03
    设[img=76x21]18039b16874949f.png[/img],其中具有[img=87x25]18039b168f9d28a.png[/img]连续偏导数,则[img=16x17]18039b16980b29c.png[/img]=
    A: [img=41x21]18039b16a0a533c.png[/img]
    B: [img=52x21]18039b16a8dd787.png[/img]
    C: x[img=80x27]18039b16b0d0dc3.png[/img]
    D: [img=78x27]18039b16b8f76e1.png[/img]