Solution: As x2−1=(x−1)(x+1) and x3−1=(x−1)(x2+x+1), the ideal J=<x−1> contains every element of the given ideal which are of the form f(x)(x2−1)+g(x)(x3−1),where f(x) and g(x) are polynomials in R[x], because the above can be written as (x−1)[(x+1)f(x)+(x2+x+1)g(x)].Also the ideal <x−1> is a maximal ideal because if any ideal I properly contains J, then take any polynomial p(x) in I∈/ J.By the Division algorithm in R[x], we can find polynomials q(x) and r(x) such thatp(x)=q(x−1)+r(x), with deg(r(x))<deg(x−1)=1⇒ r(x)=0, or r(x) is a non zero constant.But r(x)=p(x)−q(x)(x−1) is in I, and if the ideal I contains a nonzero constant r, then as the inverse of r belongs to the field R and hence 1 will belong to I ⇒I=R.∴ J=<x−1> is a maximal ideal and hence it is the maximal ideal containing <x2−1,x3−1>.
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