内容正文:
复习专号
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参考答案
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22
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1.C; 2.C; 3.C. 4.[-2,+∞); 5.(-1,+∞).
6.
3
:
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F(x)=f(x)+g(x)=lnx+ ax(x>0),#
F′(x)= 1x-
a
x2
=x-a
x2
(x>0).
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x>0,
$
F′(x)>0,
%
x>a,
&'
F(x)
(
(a,+∞)
)*+,-
.
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F′(x)<0,
%
0<x<a,
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F(x)
(
(0,a)
)
*+,.
.
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F(x)
/*+,-01"
(a,+∞),*+,.
01"
(0,a).
.,/45
、
65
1.B; 2.B; 3.C. 4.-12e; 5.13,4.
6.
3
:(1)
$
f′(-1)=f′(1)=0,
%
3a+2b+c=0,3a-2b+c=0.
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f(1)=-1,
&'
a+b+c=-1.
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a= 12,b=0,c=-
3
2.
(2)
$
(1)
2%
f(x)= 12x
3-32x,
&'
f′(x)= 32x
2-32 =
3
2(x-1)(x+1).
3
x<-1
4
x>1
5
,f′(x)>0;
3
-1<x<1
5
,f′(x)<0.
&'67
f(x)
(
(-∞,-1)8(1,+∞))9-67,(
(-1,1)
)".67
.
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x=-1
5
,f(x)
;%<=>
f(-1)=1;
3
x=1
5
,
f(x)
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f(1)=-1.
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1.A; 2.C; 3.B. 4.4槡S; 5.
3
2R.
6.
3
:
@
AN=xm.
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DN
AN=
DC
AM,&'AM=
3x
x-2.
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AMPN
/CD
S=AN·AM= 3x
2
x-2.
S′=6x(x-2)-3x
2
(x-2)2
=3x(x-4)
(x-2)2
,
3
x∈[3,4]5,S′≤
0,
&'67
S= 3x
2
x-2([3,4])".67.
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,
3
x=3
5
,S
;%E=>"
27m2,
F5
AN=3m,
AM=9m.
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AM=9m,AN=3m
5
,
ABGH
AMPN
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=
,
E=CD"
27m2.
!
22
"+,=>?@AB;
C
、
DE;
1~6 DAA CAB
F
、
GH;
7.4x-y-3=0; 8.32,-2716; 9.②③.
I
、
3);
10.
JK
:
@
f(x)=ln(x+1)-x+12x
2,
#
f′(x)= 11+x-1+x=
x2
1+x.
3
x>-1
5
,f′(x)>0.
&'
f(x)
(
(-1,+∞))9-67.
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x>0
5
,f(x)>f(0)=0.
&'3
x>0
5
,
JKL
ln(x+1)>x-12x
2.
11.
3
:
MNO2%
y= 82 ×400+2x×2×200+2×
4
x
×2×200=800x+3200x +1600(x>0),
&'
y′=800-3200
x2
.
P
y′=0,
Q%
x=2
4
x=-2(
!"
).
3
0<x<2
5
,y′<0;
3
x>2
5
,y′>0.
&'3
x=2
5
,
RST
y
;%E?>
,
E?RST"
800
×2+32002 +1600=4800(#).
12.
3
:f′(x)=3x2-x-2=(3x+2)(x-1).
P
f′(x)=0,
Q%
x=-234x=1.
3
x
UV5
,f′(x),f(x)
/UVWXYZ[
:
x -1,-[ )23 -23 -23,( )1 1 (1,2]
f′(x) + 0 - 0 +
f(x) $%& $'&
&'67
f(x)
(
x=-23\;%<=>f-( )23 =
22
27+
k;
(
x=1
\;%<?>
f(1)=k-32.
!"
f(2)=2+k,f(-1)= 12 +k,
&']^2_
f(2)=2+k
"E=>
.
`a
f(x) -k2 <0,x∈ [-1,2]b c d,e f
k2 >2+k,
Q%
k<-1
4
k>2.
:
k
/;>gh"
(-∞,-1)∪(2,+∞).
!
22
"+,LM=>NOAB;
C
、
DE;
1~12 DBCDAC DBADDA
F
、
GH;
13.0; 14.(-∞,-1); 15.8; 16.-152.
I
、
3);
17.
3
:(1)
!"
y=xlnx+1,
&'
y′=1×lnx+x· 1x
=1+lnx.
(2)k=y′|x=1=ln1+1=1,i3x=15,y=1,&'
jk"
(1,1),
&'jlmn"
y-1=1×(x-1),
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