MathOverflow will be down for maintenance for approximately 3 hours, starting Monday evening (06/24/2013) at approximately 9:00 PM Eastern time (UTC-4).

4 fixed grammar

When we write tensorial tensor products, its it's optional to indicate the ring over which we do it; we can write M⊗N  ⊗ N or M ⊗R N. But for elements, we always type write x⊗y  ⊗ y without reference to R. You must rest keep it in mind and that can induces lapsusinduce lapses. For example, v⊗u ⊗ u2-  u⊗uv maybe  ⊗ uv may be ≠0: It it depends of on the base ring, and it don´t that doesn't appear [in the notation].

Sometimes the problem it is not the concept like so much as the notation we use for it.

3 added 81 characters in body; edited body; edited body

When we write tensorial products, its optional indicate the ring over we do it; we can write M⊗N or M⊗RN. But for elements we always type x⊗y without reference to R. You must rest it in mind and that can induces lapsus. For example v⊗u2-u⊗uv maybe ≠0: It depends of the base ring, and it don´t appear.

Sometimes the problem it is not the concept like the notation we use for it.

2 added 4 characters in body