题目内容
已知直四棱柱的底面是边长为a的正方形,高为h,体积为V,表面积等于S.
(1)当a=2,h=3时,分别求V和S;
(2)当V=12,S=32时,求
+
的值.
(1)当a=2,h=3时,分别求V和S;
(2)当V=12,S=32时,求
| 2 |
| a |
| 1 |
| h |
(1)当a=2,h=3时,
V=a2h=12;
S=2a2+4ah=32;
(2)∵a2h=12,2a(a+2h)=32,
∴h=
,(a+2h)=
,
∴
+
=
=
=
.
V=a2h=12;
S=2a2+4ah=32;
(2)∵a2h=12,2a(a+2h)=32,
∴h=
| 12 |
| a2 |
| 16 |
| a |
∴
| 2 |
| a |
| 1 |
| h |
| 2h+a |
| ah |
| ||
a
|
| 4 |
| 3 |
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