Exercise
Suppose R is a domain
and a, b 
R
satisfy
Which of the following conclusions is justified?
a = 0.
a = 0, a = b, or a = -b.
None of the above.
No, there are more solutions.
Correct.
As R is a domain, there are no more solutions. Rewrite the
equation as
a3(a + b)(a - b) = 0
and use that R is a domain.
No.