The  command EvaluateAtOrigin(u) returns the image of the univariate polynomial u modulo  the maximal ideal of the ring of power series of the coefficients of u. In other words, the command EvaluateAtOrigin(u)  returns a univariate polynomial (over the complex numbers) obtained from u by specializing to zero every variable in the coefficients of u.

When using the MultivariatePowerSeries package, do not assign anything to the variables occurring in the power series and univariate polynomials over power series. If you do, you may see invalid results.

$\mathrm{with}\left(\mathrm{MultivariatePowerSeries}\right)\:$

$f≔\mathrm{UnivariatePolynomialOverPowerSeries}\left(\left(z-1\right)\left(z-2\right)\left(z-3\right)+x\left(z^2+z\right)\,z\right)\:$

$\mathrm{EvaluateAtOrigin}\left(f\right)$

$z^3-6z^2+11z-6$

$g≔\mathrm{UnivariatePolynomialOverPowerSeries}\left(y^2+x^2+\left(y+1\right)z^2+z^3\,z\right)\:$

$\mathrm{EvaluateAtOrigin}\left(g\right)$

$z^3+z^2$

The MultivariatePowerSeries[EvaluateAtOrigin] command was introduced in Maple 2021.

For more information on Maple 2021 changes, see Updates in Maple 2021.