15.求下列函数的极值.-|||-(1) (x,y)=(x)^3-4(x)^2+2xy-(y)^2+3 ;-|||-(2) (x,y)=3xy-(x)^3-(y)^3 ;-|||-(3)f (x,y)=(e)^2x(x+(y)^2+2y) ;-|||-(4) (x,y)=(6x-(x)^2)(4y-(y)^2) ;-|||-(5) (x,y)=4(x-y)-(x)^2-(y)^2 ,-|||-(6) (x,y)=xy+dfrac (8)(x)+dfrac (27)(y) .-|||-(7) (x,y)=(e)^x-y((x)^2-2(y)^2 );-|||-(8) (x,y)=(x)^3+(y)^3-3((x)^2+(y)^2) .

求函数(x,y)=(x)^3-(y)^3+3(x)^2+3(y)^2-9x-|||-__的极值求函数的极值

8.求下列函数的极值点:-|||-(1) =3axy-(x)^3-(y)^3(agt 0) ;-|||-(2) =(x)^2-xy+(y)^2-2x+y ;-|

求函数(x,y)=(x)^3-(y)^2+6y-3x的极值.求函数的极值.

[题目]求函数 (x,y)=1|2(x)^2-4xy+9(y)^2+3x-14y+-|||-1/2 的极值

求函数=(x)^2+2xy+3(y)^2-4x-|||-__的极值求函数的极值

求下列函数的极值点： (1)z=3axy-x^3-y^3(a>0); (2)z=x^2-xy+y^2-2x+y; (3)z=e^2x(x+y^2+2y).8.

[单选题]已知函数的全微分df(x,y)=(3x2+4xy-y2+1)dx+(2x2-2xy+3y2-1)dy，则f(x,y)等于（　　）.A.B.C.D.

[单选题]已知函数的全微分df(x,y)=(3x2+4xy-y2+1)dx+(2x2-2xy+3y2-1)dy，则f(x,y)等于（　　）.A.B.C.D.

[单选题]已知函数的全微分df(x,y)=(3x2+4xy-y2+1)dx+(2x2-2xy+3y2-1)dy，则f(x,y)等于（　　）.A.B.C.D.

已知函数 =(x)^3y+3(x)^2(y)^2-x(y)^3 ,则 =(x)^3y+3(x)^2(y)^2-x(y)^3 ( ) A =(x)^3y+3