Originally Posted by

**WangTaoSG** Dear All,

Need your helps desperately! I have no idea how to solve this equation, or even don't know if the solution exists at all. Can you help me? Or relate me to books or topics for this type of equations?

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Let f(x,y) be known, find function v(x)=? such that:

v[f(x,y)]=v(x)*(df/dx)+w(y)*(df/dy)

Where w(y) can be selected arbitrarily so that v(x) does exist.

Note: v(x) is function of x only, w(y) is function of y only and can be choosed by usere to ensure existence of v(x). df/dx and df/dy are partial derivatives of x and y respectively.

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Thanks very much for your help indeed!!!