y=1/2loga(a²x)loga(ax) 2≤ x≤4=1/2(loga(a²)+loga(x))loga(ax)=1/2(2+loga(x))(1+loga(x))设loga(x)=t 它的范围是[loga,2;loga,4]或者[loga,4;loga,2]这与a与1的比较来定y=1/2(2+t...