Question

下面表达式中肯定不是某个二元函数的全微分的是 A ydx+xdy B ydx-xdy C xdx+ydy D xdx-y

Answer 1

答案应该是B

答案A举例：f(x,y)=xy

答案C举例：f(x,y)=0.5 x^2 +0.5 y^2

答案C举例：f(x,y)=0.5 x^2 -0.5 y^2