Let R be a ring with identity. If ab and a are units in R, prove that b is a unit.

Advanced Engineering Mathematics
10th Edition
ISBN:9780470458365
Author:Erwin Kreyszig
Publisher:Erwin Kreyszig
Chapter2: Second-order Linear Odes
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Abstract algebra
4- Let R be a ring with identity. If ab and a are units in R, prove that b is a unit.
5- Let G and H be groups, and let f: G →H be a homomorphism. Define Ker f= {xeG; f(x):
en}. Show that Ker f is a normal subgroup of G, and that if f is one to one function then Ker f=
{eg}
6 – Let L be the set of all positive real numbers. On L define the two operations O and ®, by
aOb = ab, and a®b= alogb. Show that (L,O, ®) is a commutative ring.
Transcribed Image Text:4- Let R be a ring with identity. If ab and a are units in R, prove that b is a unit. 5- Let G and H be groups, and let f: G →H be a homomorphism. Define Ker f= {xeG; f(x): en}. Show that Ker f is a normal subgroup of G, and that if f is one to one function then Ker f= {eg} 6 – Let L be the set of all positive real numbers. On L define the two operations O and ®, by aOb = ab, and a®b= alogb. Show that (L,O, ®) is a commutative ring.
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