I hope this helps you
1.1)ОДЗ: cosx>0
1.2)ОДЗ: х>0
x=/=1 (=/= неравно)
2.1. ОДЗ:х>0
Lim x->1(1-x)(1+x+x^2)/1-x=Lim x->1 1+x+x^2=1+1+1=3
1 + Cos8x = 2Cos4x
2Cos²4x - 2Cos4x = 0
Cos²4x - Cos4x = 0
Cos4x(Cos4x - 1) = 0
1) Cos4x = 0
2) Cos4x - 1 = 0
Cos4x = 1