（log{a}(b)）^3+2(log{a}(b))^2-3log{a}(b)>0
⇔
log{a}(b) * (log{a}(b) + 3) * (log{a}(b) - 1) > 0
-3 < log{a} < 0 , 1 < log{a}(b)