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2d
comment How to Read Michael Artin's Algebra
I cannot tell what in this question is specific to Artin's book. You have to develop your best way of reading a book, and of taking notes —what is good for me is mostly irrelevant for you! Also, yes: some exercises do take a lot of time.
Sep
17
comment Necessary and sufficient condition for a ring homomorphisms property
Can you prove that that condition works?
Sep
17
comment Self-injective ring but not semisimple?
This is not correct: since $\mathbb Q$ has no non-zero proper ideals, that would mean that $I$ must be $\mathbb Q$, so that $R$ has no proper non-zero ideals, and that conclusion is false.
Sep
17
comment Self-injective ring but not semisimple?
Your description of the ideals of $R$ is not correct.
Sep
17
comment Self-injective ring but not semisimple?
What exactly have you tried to do in order to solve (1), for example? Your point (2) is missing something, as it does not mean anything as it is now.
Sep
16
comment Find matrices $ A, B$ such that $AB - BA = I$.
@HassanMuhammad, there is a well known meaning for the characteristic of a field. Google for the wikipeda page.
Sep
16
comment Find matrices $ A, B$ such that $AB - BA = I$.
Search the site for this question. It's been answered before.
Sep
16
comment Generators of ideal of coordinate axes in A^3
I don't understand your answer.
Sep
15
comment Properties of Group representations, duality and the derived subgroup
For an example, consider any non-trivial one-dimensional complex representations of a cyclic group of order three.
Sep
15
comment Cross Ratio is positive real if four points on a circle
If you actually meant that the number is positive, then well, that is not true.
Sep
15
answered Cross Ratio is positive real if four points on a circle
Sep
15
comment Consider the equation $x^4-5x^3+2x^2-5x+1=0$
It is not «positive or negative $i$»: that simply makes no sense. What you mean is $i$ or $-i$.
Sep
15
comment degree of morphism of schemes
The most shocking example of your remark, for me, is the way algebraic geometers have generalized the meaning of "local" so as to trivialize things. It is a great accomplishment :-)
Sep
15
comment Is an elementry abelian group a non-degenerate symplectic vector space?
That is not a bilinear form.
Sep
14
comment When p groups are cyclic?
@QuangHoang, but the maximal subgroup does have index $p$, precisely by hypothesis.
Sep
13
revised Curve in union of hyperplanes
added 116 characters in body
Sep
13
comment Curve in union of hyperplanes
Well, your deleted comment, which you added when I asked for clarification, clarified the question into something else! :-)
Sep
13
answered Curve in union of hyperplanes
Sep
13
comment Curve in union of hyperplanes
Please edit the question so that it asks the actual question you wanted to ask.
Sep
13
comment Curve in union of hyperplanes
Ok. This does not answer the question as amended by on of the comments...