a(a^2+3a+2)-2-2a>0
a(a+1)(a+2)-2(1+a)>0
a(a+1)(a+2)>2(a+1)
If a+1>0 => a>-1
a(a+2)>2
a^2+2a>2
a^2+2a+1>3
(a+1)^2>3
a>3^(1/2)-1
If a+1 a