代名詞 10 Posted March 7, 2008 Report Share Posted March 7, 2008 1.設a.b為正實數,已知log7 a=11 log7 b=13 問log7 (a+b)之值最接近何數?2.設a=log2 12^1/3 b=log3 0.7 c=log7 5 d=log4 5 試比較a.b.c.d之大小?對數函數的比大小現在讓我有點困擾... 尤其遇到底數或真數不同 有點不知道該如何比起?畫圖案也不會很精確 除了增減函數一看就知以外 有點苦手... Link to post Share on other sites
Zeta 10 Posted March 7, 2008 Report Share Posted March 7, 2008 參考書都有寫，我自Ｄ Link to post Share on other sites
chpohoa1 10 Posted March 7, 2008 Report Share Posted March 7, 2008 1.a=7^11,b=7^13a+b = 50 * 7^11log7 (a+b) = (log7 50) + 11 = 13..多一些 Link to post Share on other sites
Zeta 10 Posted March 7, 2008 Report Share Posted March 7, 2008 我4樓的回覆請版主刪吧，樓上有解第一題了，我不小心跟他重複了 Link to post Share on other sites
代名詞 10 Posted March 8, 2008 Author Report Share Posted March 8, 2008 所以說不同底數 或者真數要換底嗎? 畢竟這跟指數函數不同 (那邊學的挺順手的說...)感謝解答!! Link to post Share on other sites
Zeta 10 Posted March 8, 2008 Report Share Posted March 8, 2008 請自己多思考，我自Ｄ Link to post Share on other sites
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