3х - 7 = Х - 11
3х - Х = - 11 + 7
2х = - 4
Х = - 2
•••••••••••
4 - 3х = 3
3х = 4 - 3
3х = 1
Х = 1/3
12a-6x-3ax+4-25=0
(12a-21)=x(3a+6)
x=3(4a-7)/3(a+2)=(4a-7)/(a+2)
0,9x-0,6x-0,3=6
0,3x=6,3
x=6,3:0,3=21
(4a-7)/(a+2)=21
4a-7=21(a+2),a≠-2
4a-7=21a+42
21a-4a=-7-42
17a=-49
a=-49/17
<span>Cos^2x-Sin^2x=Cosx-Sinx
</span><span>Cos^2x-Sin^2x -( Cosx-Sinx) = 0
</span>(Cosx - Sinx)(Cosx + Sinx) - (Cosx -Sinx) = 0
(Cosx -Sinx)(Cosx +Sinx -1) = 0
Cosx - Sinx = 0|:Cosx или Cosx +Sinx -1 = 0
1 - tgx = 0 (1 - tg²x/2) /(1 + tg²x/2) + 2tgx/2/(1 + tg²x/2) = 1
x = π/4 + πk , k ∈Z 1 - tg²x/2 + 2tx/2 = 1 + tg²x/2
2tg²x/2 -2tgx/2 -1 = 0
tgx/2 = (1 +-√3)/2
x/2 = arctg((1 +-√3)/2) + πn, n∈Z
x = 2 arctg((1 +-√3)/2) + πn, n∈Z