Let R = Z + √2 Z and S = the ring of 2 x 2
matrices of the form [
a 2b
b. a
. ] Where a,b belongs to Z
Show that f : R --> S defined by
f (a + √2 b) = [
a. 2b
b. a
] is an isomorphism of rings.
1
Expert's answer
2020-11-24T16:53:11-0500
Surjectivity is obvious since S is the set of matrices of that special form.
Injectivity: f(a+2b)=f(c+2d). Hence, equating the columns of the matrices we get, a=c,b=d. Hence injective.
Homomorphism: f[(a+2b)+(c+2d)]=f[a+c+2(b+d)]=[a+cb+d2b+2da+c].=[ab2ba]+[cd2dc]=f(a+2b)+f(c+2d). Also f[(a+2b)(c+2d)]=f[ac+2bd+2(bc+ad)]=[ac+2bdbc+ad2bc+2adac+2bd].=[ab2ba][cd2dc]=f(a+2b)f(c+2d). Also f(1)=[1001] . Hence homomorphism
Comments