- #1
PsychonautQQ
- 784
- 10
Homework Statement
find the inverse of r in R = F[x]/<h>.
r = 1 + t - t^2
F = Z_7 (integers modulo 7), h = x^3 + x^2 -1
Homework Equations
None
The Attempt at a Solution
The polynomial on bottom is of degree 3, so R will look like:
R = {a + bt + ct^2 | a,b,c are elements of z_7 and x^3 = 1 - ^2}
To solve this problem I realized that the inverse must obviously have the form of some element in R, so I set up:
(a + bt + ct^2)(1 + t - t^2) = 1
then I multiplied it all out whilst continuously substituting for t^3 and then solving for coefficients where the constant coefficient should equal 1 and the other two should equal 0.
I did all of this and got the constant coefficient to be zero and nonzero answers for the other two >.<. I checked my calculations and can't find an error (doesn't necessarily mean there isn't one...), is something wrong with the way I set up the problem? is my substitution for x^3 correct?