# Answer to Question #23465 in Algebra for john.george.milnor

Question #23465

Let A,B be left (resp. right) ideals in a semiprime ring R. Show that AB = 0 iff BA = 0.

Expert's answer

It suffices to prove the “only if”part, so assume AB = 0, where A

(BA)^2 = BABA = 0

so BA = 0 since

*,*B are (say) left ideals. We have(BA)^2 = BABA = 0

*,*so BA = 0 since

*R*issemiprime.
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