The rule is if the terms are the same up to a rational (or floating point) coefficient, then they are combined. So for example,
>>> x + 2*x 3*x The coefficients are 1 and 2, respectively, and the remainder is x in each case, so they are combined. >>> 1/x + 2/x 3/x Same thing. >>> 1/x + 2/y 1/x + 2/y The coefficients are 1 and 2, but the rest for the first is 1/x and the rest for the second is 1/y. A similar rule is applied for multiplication and powers. x**a*x**b is combined to x**(a + b) only if a and b are the same, up to a rational/floating point coefficient. Aaron Meurer On Wed, Jun 12, 2013 at 10:27 AM, Chris Smith <smi...@gmail.com> wrote: > together brings terms together over a common denominator as the docstring > explains. If you are just adding or subtracting terms this is not an > automatic operation unless both terms are Rationals, hence > > 1/2 + 1/3 -> 5/6 but 1/x + 1/y -> unchanged > > /c > > -- > You received this message because you are subscribed to the Google Groups > "sympy" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to sympy+unsubscr...@googlegroups.com. > To post to this group, send email to sympy@googlegroups.com. > Visit this group at http://groups.google.com/group/sympy?hl=en-US. > For more options, visit https://groups.google.com/groups/opt_out. > > -- You received this message because you are subscribed to the Google Groups "sympy" group. To unsubscribe from this group and stop receiving emails from it, send an email to sympy+unsubscr...@googlegroups.com. To post to this group, send email to sympy@googlegroups.com. Visit this group at http://groups.google.com/group/sympy. For more options, visit https://groups.google.com/groups/opt_out.
