2 ms·
Well, it does double the residue: 20 * 2 === 40 === 2 (mod 19) 21 * 2 === 42 === 4 (mod 19) 18 * 2 === 36 === 17 (mod 19), equivalently -1 * 2 === -2 === 17
by MauranKilom 6y ago
Well, it does double the residue:
20 * 2 === 40 === 2 (mod 19)
21 * 2 === 42 === 4 (mod 19)
18 * 2 === 36 === 17 (mod 19), equivalently -1 * 2 === -2 === 17 (mod 19)
10 * 2 === 20 === 1 (mod 19), equivalently -9 * 2 === -18 === 1 (mod 19)