-3х+2=2х+7
-3x-2x=7-2
-5x=5
x=-5/5
x=-1
_____________
3х^2у-9ху^2=3xy(x-3y)
-7(а-4)-5(а-8)=86
-7а+28-5а+40=86
-12а=18
а=-1,5
Таблица во вложении................
Cos(π/6 - 2x) = - 1
cos(2x - π/6) = - 1
2x - π/6 = π + 2πk, k∈Z
2x = π/6 + π + 2πk, k∈Z
2x = 7π/6 + 2πk, k∈Z
x = 7π/12 + πk, k∈Z