(x+3)^3+(x-5)^3>=2(x-1)^3
x-1=t
x+3=x-1+4=t+4; x-5=x-1-4=t-4
(t+4)^3+(t-4)^3>=2t^3
2t^3+6t*14>=2t^3
84t>=0
t>=0
x-1>=0
x>=1
xЄ[1;+беск)