Find the multiplicative inverse of x^2+(x^3−x+2) in the quotient F_3[x]/(x^3−x+2)

Zachariah Norris

Zachariah Norris

Answered question

2022-09-18

Find the multiplicative inverse of x 2 + ( x 3 x + 2 ) in the quotient F 3 [ x ] / ( x 3 x + 2 )

Answer & Explanation

zmikavtmz

zmikavtmz

Beginner2022-09-19Added 5 answers

You wrote you can find f,g such that ... and that's what you need to do. This is just th e(extended) Euclidean algorithm as known from integers, but requiring polynomial divisions. Thius
x 3 x + 2 = x x 2 ( x 2 ) x 2 = ( x 2 ) x + 2 x x 2 = 2 x 1 2 2 = 2 x 2 + 1
(where only the last step is aware of us working in F 3 ). From this with p ( x ) = x 3 x + 2 , q ( x ) = x 2 we obtain step by step:
x 2 = x q p 2 x = q x ( x q p ) 1 = ( x q p ) 2 ( q x ( x q p ) )
So
( x + 2 ) p ( x ) + ( 2 x 2 + x + 1 ) q ( x ) = 1

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