Plücker formula and the equisingularity set of a linear system Quadratic transformations of the elliptic differential 
\[
\frac {\sum\pm c_1 x_2 dx_3}{c_1 \frac {\partial f}{\partial x_1} +c_2 \frac {\partial f}{\partial x_2} + c_3 \frac {\partial f}{\partial x_3}}
\]
 under the assumption \(f(xxx)=0\). 