1. Ler R be a ring, and , prove, using axioms for a ring, the following
The identity element of R s unique
That -r is the unique element of R such tht (-r)+r = 0.
(hint, for part 1, suppose that 1 and 1' ate two identities of R, show that 1-1' must be zero, and for part 2, suppose that there is an element such that s+r = 0, and prove that s = -r)
2. let R be the set of complex 4th roots of 1. so R = {1,-1,i,-i} . Does R, together with the usual addition and multiplication of complex numbers, form a ring? Justify your answer.
3.
Let R be the ring . Show that is a subring but not an ideal of R.
Let R be a ring. Define what is meant by a polynomial over R in the inderminate x.
4. let and be polynomials in . Calculate f + g and fg in .