Re: [中學] 對數
※ 引述《m87917739 (mel)》之銘言：
: 第二題
: http://imgur.com/a/XhILN
u = log_2 (α)
α = 2^u
u + 2^u - 4 = 0
2^β + β - 4 = 0
=> β = u = log_2 (α)
=> α + β = 2^u + β
= 2^β + β = 4
: 第三題
: http://imgur.com/a/KSEQ8
顯然y=/=0
=> x = 1
=> z = 1/3
=> y = (1/2)^3 = 1/8
=> xyz = 1/24
: 第四題
: http://imgur.com/a/JwUKA
a + 1/a = 4
=> a = 2 + √3, 2 - √3
(1/a)^4 - 8(1/a)^3 + 16(1/a)^2 + 5
= (1/a)^2 [1/a - 4]^2 + 5
= (1/a)^2 * a^2 + 5
= 6
: 第五題
: http://imgur.com/a/6uUSh
2xlog(1.008) > log2
=> x > log(2) / [2 * log(1.008)]
: 麻煩大家幫忙！
: 完全忘記對數怎麼計算了....
: 謝謝!!!!
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