sup = support f
Returns the variables appearing in f (as elements of the ring of f).
i1 : A = QQ{x,y,z,w} o1 = A o1 : NCPolynomialRing
i2 : f = x^2+y^2+z^3 3 2 2 o2 = z +y +x o2 : A
i3 : sup = support f o3 = {y, x, z} o3 : List
i4 : first sup o4 = y o4 : A