[線代]關於此題的某一步...

17^-1 (mod 1009) = ?
1009 = 59 * 17 +6
17 = 2 * 6 + 5
6 = 1 * 5 + 1

1= 6 - 1 * 5
= 6-(17-2*6)
=-17 + 3 * 6 請問這段是如何出來的呢??
= -17 + 3 *(1009-59*17)
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