求函数y=(log2 4/x)(log4 x/32)在定义域【1/2,8】的值域

y=[log2(4)-log2(x)][log4(x)-log4(32)]=[2-log2(x)](lgx/lg4-lg32/lg4)=[2-log2(x)](lgx/2lg2-5lg2/2lg2)=[2-log2(x)][1/2*log2(x)-5/2]令a=log2(x)1/2