I need some help from our resident math genius posters. I am working on my discrete stuff and I need help with the following problem

find the gcd of a = -1575 and b = 231, write it in the form alphaX + betab, where alpha , B belong to Z.

we were taught a method like this

-1575 1 0
231 0 1

then find q ( a/b floored if b>o and take the ceiling if b<0)
then r which is : a-qb

and then that makes the next row with the numbers under the 0 and 1 are found by such (1-q(0), and 0-q(1)... the 1 in the first part is from the first row second column and the zero is from the second row second column) Then same idea for the next number. and that method is used down the line.

its hard to explain I guess... I need to do good on this homework so it helps my grade. If anything I can scan in the sheet.