Ò»¡¢Ñ¡ÔñÌâ(ÿСÌâ5·Ö£¬¹²20·Ö)
1£®(2013•Äþ²¨Ä£Äâ)Èôa£¾0£¬b£¾0£¬ÇÒa£«2b£­2£½0£¬ÔòabµÄ×î´óֵΪ (¡¡¡¡)£®¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡
A.12 B£®1 C£®2 D£®4
½âÎö¡¡¡ßa£¾0£¬b£¾0£¬a£«2b£½2£¬∴a£«2b£½2≥22ab£¬¼´ab≤12.µ±ÇÒ½öµ±a£½1£¬b£½12ʱµÈºÅ³ÉÁ¢£®
´ð°¸¡¡A
2£®º¯Êýy£½x2£«2x£­1(x>1)µÄ×îСֵÊÇ (¡¡¡¡)£®
A£®23£«2 B£®23£­2
C£®23 D£®2
½âÎö¡¡¡ßx>1£¬∴x£­1>0£¬
∴y£½x2£«2x£­1£½x2£­2x£«1£«2x£­1£«3x£­1
£½x£­12£«2x£­1£«3x£­1£½(x£­1)£«3x£­1£«2≥23£«2.
µ±ÇÒ½öµ±x£­1£½3x£­1£¬¼´x£½3£«1ʱȡµÈºÅ£®
´ð°¸¡¡A