Multiplication in $\mathbb {Z}$/p$\mathbb {Z}$ or in $\mathbb {Z}$/p$\mathbb {Z}$[x] : *

* multiplies two integers in $\mathbb {Z}$/p$\mathbb {Z}$ or two polynomials in $\mathbb {Z}$/p$\mathbb {Z}$[x]. For polynomial expressions, use the normal command to simplify.
For integers in $\mathbb {Z}$/p$\mathbb {Z}$, input :

31%13*10%13

Output :

-2%13

For polynomials with coefficients in $\mathbb {Z}$/p$\mathbb {Z}$, input :

normal((11*x+5)%13*(8*x+6 )% 13)

or also :

normal((11% 13*x+5%13)*(8% 13*x+6%13))

Output :

(-3%13)*x^2+(2%13)*x+4%13