roots takes as arguments a symbolic
polynomial expression and the name of its variable.
roots returns a 2 columns matrix : each row is
the list of a root of the polynomial and its multiplicity.
Examples
^
5-2*x^
4+x^
3) ^
10-15*x^
8+90*x^
6-270*x^
4+405*x^
2-243)^
3-1,t)