click below
click below
Normal Size Small Size show me how
abstract
before second test
Question | Answer |
---|---|
additive identity | a+o=a |
multiplicative identity | ax=1 |
additive inverse | a+x=o |
multiplicative inverse | [a][n]=1 |
subring | ring closed under multiplication and subtraction |
commutative ring | xy=yx |
unity | multiplicative identity |
units | ab=ba=1 (a is a unit) |
zero divisor | R is a commutative ring, a does not equal 0, b does not equal 0, ab=0 |
integral domain | commutative ring but has no zero divisors |
field | commutative ring with unity in which every non-zero element is a unit |
factor of a polynomial | something you can factor out with remainder 0 |
root of a polynomial | plug in that number and get 0 |
Theorem 8.1 | Suppose R is an integral domain and a,b,c are elements of R with a not equal to 0. If ab=ac, then b=c |
Theorem 8.2 | A field has no zero divisors |
Theorem 8.5 | Zn is a field iff n is prime |
Theorem 8.6 | Let o less than x less than m. Then [x] is a unit in the ring Zm iff gcd (x,m)=1 |
Theorem 8.8 | All finite domains are fields |
examples of finite fields | Z5, Z3, Z2 |
examples of infinite field | Q |
finite integral domain that's not a field | impossible |
infinite integral domain that's not a field | Z |
a set that is closed under multiplication but not subtraction | N |
field without unity | impossible |
ring without unity | 2Z (even integers) |
polynomial in Q[x], reducible in Q[x] but has no roots in Q | x^4 -4 |