å·²ç¥å½æ°f(x)=lnx,g(x)=2-(3/x)(x>0)ï¼(1).å¤æf(x)ä¸g(x)ç大å°å
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解ï¼(1)ãf(1)=0ï¼g(1)=2-3=-1ï¼xâ+âæ¶f(x)â+âï¼èg(x)â2ï¼xâ0æ¶f(x)â-â
g(x)â-âï¼æ
å¯ä»¥å¤æï¼å¨x>0æ¶ï¼f(x)>g(x)ï¼
(2)ã令f '(x)=1/x=g'(x)=3/x²ï¼å¾x²-3x=x(x-3)=0ï¼æ
å¾x₁=0ï¼x₂=3ï¼
å½x=0æ¶f(x)ä¸g(x)é½æ å®ä¹ï¼æè
说ï¼x=0,å³yè½´æ¯ä¸¤ä¸ªå½æ°çæ¸è¿çº¿ãä½ä¸æ¯å
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(3ï¼g(3))çå线äºç¸å¹³è¡ï¼ä½ä¸æ¯å
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