Resultant

Functions

void fmpq_poly_resultant (mpq_t rop, const fmpq_poly_ptr a, const fmpq_poly_ptr b)
 Returns the resultant of a and b.Returns the resultant of a and b.

Function Documentation

void fmpq_poly_resultant ( mpq_t  rop,
const fmpq_poly_ptr  a,
const fmpq_poly_ptr  b 
)

Returns the resultant of a and b.Returns the resultant of a and b.

Enumerating the roots of a and b over $\bar{\mathbf{Q}}$ as $r_1, \dotsc, r_m$ and $s_1, \dotsc, s_n$, respectively, and letting $x$ and $y$ denote the leading coefficients, the resultant is defined as

\[ x^{\deg(b)} y^{\deg(a)} \prod_{1 \leq i, j \leq n} (r_i - s_j). \]

We handle special cases as follows: if one of the polynomials is zero, the resultant is zero. Note that otherwise if one of the polynomials is constant, the last term in the above expression is the empty product.

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