How are these terms algebraically equivalent?

68 Views Asked by Bumbble Comm At 07 Apr 2026 - 7:28

This is the definition of a is congruent to b modulo m. (from slide 24)

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This is an example on the next slide, slide 25 enter image description here

I know that enter image description here is saying 17 divides A - (-1) or 17 divides A + 1, meaning

A + 1 = 17x where x is some integer, solving for A, you get

A = 17x - 1.

Where does 17x + 16 come from? Algebraically, that is not equal to 17x - 1.