y=(log1/a(a^2)+log1/a(x))*(log1/a^2(a)+log1/a^2(x))
=[-(2+loga(x))]*[-(1/2+1/2loga(x))]
=1/2(loga(x))^2+3/2loga(x)+1
令t=loga(x)
则y=(1/2)t^2+(3/2)t+1,为t的二次函数,
-b/2a=-3/2 ,(4ac-b^2)/4a=-1/8
画出y--t图象（自己画下吧）,图象开口向上,当-1/8