You must doexactlythe same as with integers when applying Euclides' Algorithm: divide and divide until you get the gcd, and then go backwards and write each remainder as a linear combination of the other stuff...

And we're done since the remainder now is a unit (i.e., the reaminder is 1), so now go backwards (some parentheses are for clearity's sake):

Of course, instead you can write

Tonio