Minor review changes

Author: jdemeyer

src/sage/rings/polynomial/multi_polynomial_libsingular.pyx

@@ -4046,7 +4046,7 @@ cdef class MPolynomial_libsingular(sage.rings.polynomial.multi_polynomial.MPolyn
             ...
             NotImplementedError: Factorization of multivariate polynomials over prime fields with characteristic > 2^29 is not implemented.
 
-        Factorization over the integers is now supported, see :trac:`17840` ::
+        Factorization over the integers is now supported, see :trac:`17840`::
 
             sage: P.<x,y> = PolynomialRing(ZZ)
             sage: f = 12 * (3*x*y + 4) * (5*x - 2) * (2*y + 7)^2
@@ -4055,6 +4055,8 @@ cdef class MPolynomial_libsingular(sage.rings.polynomial.multi_polynomial.MPolyn
             sage: g = -12 * (x^2 - y^2)
             sage: g.factor()
             (-1) * 2^2 * 3 * (x - y) * (x + y)
+            sage: factor(-4*x*y - 2*x + 2*y + 1)
+            (-1) * (2*y + 1) * (2*x - 1)
 
         Factorization over non-integral domains is not supported ::