题目内容
若△ABC三边的长a,b,c均为整数,且
+
+
=
,a+b-c=8,设△ABC的面积为S,则S的最大值是______,最小值是______.
1 |
a |
1 |
b |
3 |
ab |
1 |
4 |
∵由
+
+
=
可得,
4b+4a+12=ab,
ab-4a-4b=12,
∴(a-4)(b-4)=28,
∴a>4,b>4,
∴a-4=1,2,4,7,14,28,
b-4=28,14,7,4,2,1,
∴a=5,6,8,11,18,32,
b=32,18,11,8,6,5,
c=29,16,11,11,16,29,
(1)当a=5,b=32,c=29时,p=
=33,S=
=
=4
;
(2)当a=6,b=18,c=16时,p=
=20,S=
=8
;
(3)当a=8,b=11,c=11时,p=
=15,S=
=4
;
(4)当a=11,b=8,c=11时,p=
=15,S=
=4
;
(5)当a=18,b=6,c=16时,p=
=20,S=
=8
;
(6)当a=32,b=5,c=29时,p=
=33,S=
=4
.
可见最大值为4
,最小值为4
.
故答案为4
,4
.
1 |
a |
1 |
b |
3 |
ab |
1 |
4 |
4b+4a+12=ab,
ab-4a-4b=12,
∴(a-4)(b-4)=28,
∴a>4,b>4,
∴a-4=1,2,4,7,14,28,
b-4=28,14,7,4,2,1,
∴a=5,6,8,11,18,32,
b=32,18,11,8,6,5,
c=29,16,11,11,16,29,
(1)当a=5,b=32,c=29时,p=
5+32+29 |
2 |
p(p-a)(p-b)(p-c) |
33(33-5)(33-32)(33-29) |
231 |
(2)当a=6,b=18,c=16时,p=
6+18+16 |
2 |
20(20-6)(20-18)(20-16) |
35 |
(3)当a=8,b=11,c=11时,p=
8+11+11 |
2 |
15(15-8)(15-11)(15-11) |
105 |
(4)当a=11,b=8,c=11时,p=
11+8+11 |
2 |
15(15-11)(15-8)(15-11) |
105 |
(5)当a=18,b=6,c=16时,p=
18+6+16 |
2 |
20(20-18)(20-6)(20-16) |
35 |
(6)当a=32,b=5,c=29时,p=
32+5+29 |
2 |
33(33-32)(33-5)(33-29) |
231 |
可见最大值为4
231 |
105 |
故答案为4
231 |
105 |
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