1.
沒看懂logx是什么意思,又沒有底數(shù),又不是lg.
2.
對(duì)數(shù)有意義,x/2>0 x/4>0 得x>0
f(x)=[log2(x/2)]×[log2(x/4)]
=[log2(x) -1]×[log2(x) -2]
=[log2(x)]²-3log2(x)+2
=[log2(x) -3/2]² -1/4
當(dāng)log2(x)=3/2時(shí),即x=2^(3/2)時(shí),f(x)有最小值[f(x)]min=-1/4
當(dāng)log2(x)->+∞時(shí),f(x)趨向于+∞,函數(shù)沒有最大值.不好意思 對(duì)于1 是log以二為底的x的對(duì)數(shù)打錯(cuò)了2[log2(x)]²-7log2(x) +3≤0[log2(x) -3][2log2(x) -1]≤01/2≤log2(x)≤3√2≤x≤81/2≤log2(x)≤3這個(gè)怎麼得出來的呢？這是對(duì)數(shù)的基礎(chǔ)知識(shí)啊，熟練了就不用一步一步寫了。中間其實(shí)還有一步，省略了：2[log2(x)]²-7log2(x) +3≤0[log2(x) -3][2log2(x) -1]≤01/2≤log2(x)≤32^(1/2)≤x≤2³ 就是這一步√2≤x≤8