L是区域D：x²+y²≤-2x的正向周界，则（x³-y）dx+（x-y²）dy等于：（）

+2y)dx+(2x+3(y)^2)dy在整个xoy平面内是某一函数+2y)dx+(2x+3(y)^2)dy的全微分，则+2y)dx+(2x+3(y)^2)dy

解方程(x^2+y^2+3)(dy)/(dx)=2x(2y-(x^2)/(y)).解方程$(x^{2}+y^{2}+3)\frac{dy}{dx}=2x(2y-

(3)(x^2+2xy-y^2)dx+(y^2+2xy-x^2)dy=0,y|_(x=1)=1;(3)$(x^{2}+2xy-y^{2})dx+(y^{2}+2

微分方程(3x^2+6y^2x)dx+(6x^2y+4y^2)dy=0的通解是()A. $x^3+3x^2y^2+4y^2=C$B. $x^3+3x^2y^2-

已知u(x,y)=2x(1-y),则满足u(x,y)=2x(1-y)的解析函数u(x,y)=2x(1-y)为u(x,y)=2x(1-y)u(x,y)=2x(1-

设=dfrac (2x)({x)^2-(y)^2} ，则 =dfrac (2x)({x)^2-(y)^2}=dfrac (2x)({x)^2-(y)^2}___

计算 =(int )_(L)dfrac ((x-y)dx+(x+y)dy)({x)^2+(y)^2}-|||-f[(x-y)(x+(x+y)dy)/(x^2+x

[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.