2(3-х) + 7(х-4) - 5(х-1) = 3(х-4) - (3х+5),
6-2х + 7х-28 - 5х+5 = 3х-12 - 3х-5,
6 - 28 + 5 = -12 - 5,
-17 = -17 - тождество доказано
2(3-х) + 7(х-4) - 5(х-1) = 3(х-4) - (3х+5),
6-2х + 7х-28 - 5х+5 = 3х-12 - 3х-5,
6 - 28 + 5 = -12 - 5,
-17 = -17 - тождество доказано