Exercise · ZW-UNIT-OF-A-RING-004 · ★☆☆ Basic
What are the units of the ring \(\mathbb{Z}\) of integers?
Choose one option.
Show answer
- D. \(1\) and \(-1\)
Explanation
An integer \(u\) has an integer inverse \(v\) with \(uv=1\) only if \(|u|=1\), so the units are \(1\) and \(-1\). For example, \(2\) is not a unit because \(1/2\) is not an integer.
Review the concept: Unit of a ring
A unit of a ring \(R\) with identity \(1\) is an element \(u\) that has a multiplicative inverse \(v\) within \(R\).
\[uv=vu=1\]
More practice problems: unit of a ring
- ZW-UNIT-OF-A-RING-001 How many units does the ring ℤ_12 have?
- ZW-UNIT-OF-A-RING-002 Which of these elements is a unit of ℤ_10?
- ZW-UNIT-OF-A-RING-003 What is the multiplicative inverse of 5 in ℤ_17?
- ZW-UNIT-OF-A-RING-005 How many units does the ring ℤ[i]=\a+bi: a,b∈ℤ\ have?
- ZW-UNIT-OF-A-RING-006 Which of these elements is a unit of ℤ[√2]?
- ZW-UNIT-OF-A-RING-007 If u and v are units of a commutative ring with identity, which of these elements is also a unit?
- ZW-UNIT-OF-A-RING-008 In a ring with 1ne0, can the element 0 be a unit?
- ZW-UNIT-OF-A-RING-009 For which of these values of n is every nonzero element of ℤ_n a unit?