Function: ptriangularize (<M>, <v>) If <M> is a matrix with each entry a polynomial in <v>, return a matrix <M2> such that
(1) <M2> is upper triangular,
<M2> = <E_n> ... <E_1> <M>, where <E_1> through <E_n> are elementary matrices whose entries are polynomials in <v>,
|det (<M>)| = |det (<M2>)|,
Note: This function doesnt check that every entry is a polynomial in <v>.
(%o1) true (%i2)