2 X (3)n-1 = 10000(3)n-1 = 5000然後ㄋ?
2005-05-21 11:09:48 · 6 個解答 · 發問者 changchih 7 in 科學 ➔ 數學
還市不懂
2005-05-21 11:41:18 · update #1
還市不懂
2005-05-21 11:41:23 · update #2
(log以10為底的10=1 ， log以10為底的3=0.4771 ， log以10為底的5=0.6990)
(3)^(n-1) = 5000
→兩邊以3為底，取log
→log以3為底的3^(n-1)=log以3為底的(5x10^3)
→ n-1=log以3為底的(5x10^3)
→n-1=【(log以10為底的5)+(log以10為底的10^3)】/(log以10為底的3)
→n-1=(0.6990+3)/(0.4771)=7.7530915
→n=7.7530915+1=8.7530915
→n約等於8.75
2005-05-21 11:49:32 · answer #1 · answered by Anonymous · 0⤊ 0⤋
降還不懂.就請幼稚園老師來教.
3^1=3
3^2=9
3^3=27
3^4=81
3^5=243
3^6=729
3^7=2187
3^8=6561
所以5000=3^(7.753)=3要開那麼多次方.
那n是多少會了吧.
2005-05-21 17:37:18 · answer #2 · answered by WYZ 7 · 0⤊ 0⤋
建議開板的，你應該要先複習一下「指數與對數」那個章節，上面他們所回答的你自然就看的懂了。
2005-05-21 16:09:20 · answer #3 · answered by ? 2 · 0⤊ 0⤋
2*3^(n-1)=10000
3^(n-1)=5000
等式兩邊取log對數
log 3^(n-1)=log 5000
(註：log x^y=y log x)
(n-1) log 3= log 5000
(註：log 3=0.477121, log 5000=3.69897)
n-1* 0.477121 = 3.69897
n-1= 7.752683
n=8.75268
2005-05-21 12:06:26 · answer #4 · answered by hung559 5 · 0⤊ 0⤋
2 X (3)^n-1 = 10000
(3)^n-1 = 5000
3^n=3*5000
nlog3=log15000=3+log15=3+0.4771+0.6990
n*(0.4771)=4.1761
n=8.75
2005-05-21 11:38:44 · answer #5 · answered by 吉米 6 · 0⤊ 0⤋
取log 底數是10
log2+(n-1)log3=4 （3的n-1次方取log會變下來）(log10000=4)
(log2=0.3010)
(log3=0.4771)
(n-1)0.4771=4- 0.3010 (log2移向)
n-1=7.7531 (0.4771移向變分母)
n=6.7531
2005-05-21 11:34:50 · answer #6 · answered by ? 1 · 0⤊ 0⤋