<<
+<+②和④都是对的; 4 A 11(10)()1,()(10)1,(10)(10)111010f f f f f f =+=-+=-++ 5 C ()()(),()()()()(),f x g x h x f x g x h x g x h x =+-=-+-=-+
()()()()()lg(101),()222
x f x f x f x f x x h x g x +---==+==
6 C a b c =====
<==>
二、填空题 1 (1,)+∞ 2
210ax x ++>恒成立,则0440a a >???=-,得1a > 2 []0,1 2
21ax x ++须取遍所有的正实数,当0a =时,21x +符合 条件;当0a ≠时,则0440a a >???=-≥?
,得01a <≤,即01a ≤≤ 3 [)[)0,,0,1+∞ 1
1
1()0,()1,022x x x -≥≤≥;1
1
()0,01()1,22x x
>≤-< 4 2 ()()11011
x x m m f x f x a a --+=+++=-- (1)20,20,21
x x m a m m a -+=-==-
5 19 293(3)18lg1019-?-+=+=
三、解答题
1 解:(1)40.2540.25log (3)log (3)log (1)log (21)x x x x -++=-++
4
0.2543213log log log ,1321
x x x x x x -++==-++ 33121x x x x -+=-+,得7x =或0x =,经检验0x =为所求 (2)2(lg )lg lg lg lg 1020,(10)20x x x x x x x +=+=
lg lg lg 220,10,(lg )1,lg 1,x x x x x x x x +====±
10,x =1或
10,经检验10,x =1或10为所求 2 解:21111()()1[()]()14222
x x x x y =-+=-+ 2113[()],224
x =-+ 而[]3,2x ∈-,则11()842
x ≤≤ 当11()22x =时,min 34y =;当1()82
x =时,max 57y = ∴值域为3[,57]4
3 解:3()()1log 32log 21log 4
x x x f x g x -=+-=+, 当31log 04x
+>,即01x <<或43
x >时,()()f x g x >; 当31log 04x +=,即43
x =时,()()f x g x =; 当31log 04x +<,即413x <<时,()()f x g x < 4 解:(1)1121()()212221
x x x x f x x +=+=?-- 2121()()221221
x x x x x x f x f x --++-=-?=?=--,为偶函数 (2)21()221
x x x f x +=?-,当0x >,则210x ->,即()0f x >; 当0x <,则210x
-<,即()0f x >,∴()0f x >