1) \( 6a - 17a + 19a - 8a = (6 - 17 + 19 - 8)a = ( -11 + 19 - 8)a = (8 - 8)a = 0a = 0 \)
2) \( -4x + 5x + 13x - 15x = (-4 + 5 + 13 - 15)x = (1 + 13 - 15)x = (14 - 15)x = -1x = -x \)
3) \( 2a - 3b + 4a - 2b = (2a + 4a) + (-3b - 2b) = (2 + 4)a + (-3 - 2)b = 6a - 5b \)
4) \( -7x + 5y + 3x - 10y = (-7x + 3x) + (5y - 10y) = (-7 + 3)x + (5 - 10)y = -4x - 5y \)
Ответ: 1) 0; 2) -x; 3) 6a - 5b; 4) -4x - 5y.