内容正文:
9.`犳(狓)=犪狓2+犫狓+犮(犪≠0),#犳(2狓)+犳(3狓+1)=
(4犪狓2+2犫狓+犮)+[9犪狓2+(6犪+3犫)狓+犪+犫+犮]=
13犪狓2+(6犪+5犫)狓+犪+犫+2犮,U]
13犪=13,
6犪+5犫=6,
犪+犫+2犮=-1
烅
烄
烆 .
U]
犪=1,
犫=0,
犮=-1
烅
烄
烆 .
U]犳(狓)=狓2-1.
10.`犳(狓)=犪(狓-2)2-9,狓1,狓2F45犪(狓-2)
2-9
=0A�>,犪狓2-4犪狓+4犪-9=0,U]狓1+狓2=4,
狓1狓2=
4犪-9
犪
.�|狓1-狓2|=6,U](狓1+狓2)
2-
4狓1狓2=36.U]16-4×
4犪-9
犪
=36.U]犪=1.U
]犳(狓)=狓2-4狓-5.
11.(1)9
4犪+2犫+犮=4,
-
犫
2犪
=
1
2
,
狓21+狓
2
2=13
烅
烄
烆 ,
XV@
犪=-1,
犫=1,
犮=6
烅
烄
烆 ,
U]ÂK?
Ìl6狔=-狓2+狓+6,¦§Ô.
(2)9-狓2+狓+6=0,?@狓1=3,狓2=-2,uÕÖ
ׯkde��±²A犇,9犛△犃犅犆=2犛△犇犅犆,#
犇 AØÊË62,9-狓2+狓+6=2,?@狓1=
槡1+ 17
2
,狓2 =
槡1- 17
2
,
U ] 犇 + � -,f
犇1
槡1+ 17
2
,( )2 ,犇2 槡1- 172 ,( )2 .
&11' )DU+ZL-[\]
1.B
2.狔=狓2+狆狓+狇= 狓+
狆( )2
2
+狇-
狆2
4
,
U]-
狆
2
=1O
狇-
狆2
4
=3,U]狆=-2,狇=4.
3.犳(狓)= (狓-犪)2+ (狓-犫)2=2 狓-
犪+犫( )2
2
+
(犪-犫)2
2
,
U]!狓=
犪+犫
2
"
,犳(狓)=(狓-犪)2+(狓-
犫)2AÇÈC6
(犪-犫)2
2
.
4.(1)犳(狆)=-2狆2+3狆.
(2)!狆=
3
4
"
,犳(狆)+ÇÙC,�ÇÙCF
9
8
.
5.93狓+2狔=12,@狓=4-
2
3
狔,U]狓狔= 4-
2
3( )狔狔
=-
2
3
(狔-3)2+6,U]!狔=3",狓狔AÇÙC
66.
6.(1)9&',3狓+犅犆=24,U]犅犆=24-3狓,p��犛
=犅犆×犃犅=(24-3狓)狓
f犛=(24-3狓)狓=24狓-3狓2
(2)f犛=45,��@24狓-3狓2=45,?@狓=5,;狓
=3,
∵0≤24-3狓≤10
∴
14
3
≤狓≤8
∴狓=5,
f犃犅=5Ú
(3)犛=24狓-3狓2=-3(狓-4)2+48
∵犅犆AÇÙÛÜ610m,f0≤犅犆=24-3狓≤10,
∴
14
3
≤狓≤8,∴狓∈
14
3
,[ ]8 .∵MÃÄ6狓=4OÝÞ
ßv
,∴!狓=
14
3
"B@ÇÙC犛max=
140
3
,
U]LE
Q¼45m2àÙAáâ.!犃犅=
14
3
ÚA"ãB@Ç
ÙC
140
3
m2.
7.`I4·AäÛ6狓,#åAäÛ61-狓,æç狉
=
1-狓
2π
.
U]犛
I
=
狓( )4
2
=
狓2
16
,犛
å
=π·
(1-狓)2
4π2
.
犛
I
+犛
å
=
(π+4)狓2-8狓+4
16π
(0<狓<1).
U]!狓=
4
π+4
"+ÇÈC.
8.`èéê·A�nÛÀë6狓cm,狔cm,��6犛
cm2,76
狓
20
=
16-狔
16
,
U]狓=
5
4
(16-狔),U]犛=狓狔=
5
4
(16-狔)狔=
5
4
[-(狔-8)2+64],U]!狔=8cm,狓=10cm",
èéê·AÇÙ��680cm2.
9.?:(1)
ìíî¤
(
.
) 狓
ìíµ狔(²) 1000-10狓
ìíïðñ@òó狑(.) -10狓2+1300狓-30000
(2)-10狓2+1300狓-30000=10000
?�@
:狓1=50,狓2=80
ô
:
ïðìíî¤650.;80.",Xñ@10000.
ìíòó
,
(3)>³&'@
1000-10狓≥540
狓≥
{
44
?�@
:44≤狓≤46
狑=-10狓2+1300狓-30000=-10(狓-65)2+
12250
·86·
89:;<=>
∵犪=-10<0,MÃÄ狓=65
∴!44≤狓≤46",狔õ狓öÙpöÙ
∴!狓=46",狑
ÇÙC
=8640(.)
ô
:
÷øìíùúûïðñ@AÇÙòó68640.