股怪精灵
幼苗
共回答了18个问题采纳率:83.3% 举报
(1)由
![](https://img.yulucn.com/upload/3/46/346bdd61e96ed867f9ccb00436e0829b_thumb.jpg)
=0,得x=-4,
∴A点的坐标为(-4,0)
由-2x+16=0,得x=8
∴B点的坐标为(8,0)
∴AB=8-(-4)=12
由
![](https://img.yulucn.com/upload/4/58/45869165bc307a7a43881d842f86843f_thumb.jpg)
,解得
![](https://img.yulucn.com/upload/f/da/fdaaab1340e53c0768d8dce8947632b2_thumb.jpg)
,
∴C点的坐标为(5,6),
∴
![](https://img.yulucn.com/upload/a/f9/af93cd7449264d1788b85615b5554a30_thumb.jpg)
;
(2)∵点D在l
1 上且x
D =x
B =8,
∴
![](https://img.yulucn.com/upload/4/bd/4bd2158b62dd3c21977da8cd06185c90_thumb.jpg)
,
∴D点的坐标为(8,8),
又∵点E在l
2 上且y
E =y
D =8,
∴-2x
E +16=8,
∴x
E =4,
∴E点的坐标为(4,8),
∴DE=8-4=4,EF=8;
(3)①当0≤t<3时,如图(1),矩形DEFG与△ABC重叠部分为五边形CHFGR(当t=0时,为四边形CHFG)
过C作CM⊥AB于M,则Rt△RGB∽Rt△CMB,
∴
![](https://img.yulucn.com/upload/e/f3/ef36387a1243317b78567e9f8e5cecc0_thumb.jpg)
,即
![](https://img.yulucn.com/upload/7/e0/7e064b9c8bf54d95ec7527a762363bc1_thumb.jpg)
,∴RG=2t,
∵Rt△AFH∽Rt△AMC,∴
![](https://img.yulucn.com/upload/7/f0/7f034d4cb0c7e383738b1d7d33900973_thumb.jpg)
,即
![](https://img.yulucn.com/upload/8/c4/8c457e01ee0a250b605b5299174c0f37_thumb.jpg)
,
∴
![](https://img.yulucn.com/upload/4/0e/40ebd51dfdd1dcc43adf8b7c81cf9f1d_thumb.jpg)
,
∴S=S
△ABC -S
△BRG -S
△AFH =
![](https://img.yulucn.com/upload/9/59/95918594d351253d1d9096808e2cb2f6_thumb.jpg)
,
即
![](https://img.yulucn.com/upload/9/d9/9d9e77024c505a917f4334169801a5f5_thumb.jpg)
;
②当3≤t<8时,如图(2),矩形DEFG与△ABC重叠部分为梯形HFGR,过C作CM⊥AB于M,则Rt△ARG∽Rt△ACM,
∴
![](https://img.yulucn.com/upload/a/58/a583ad34a5200bb1f6f91c87b7860bcb_thumb.jpg)
,∴
![](https://img.yulucn.com/upload/1/90/190b99bd688ef8e6ed570dd0cc4cd8bd_thumb.jpg)
,∴
![](https://img.yulucn.com/upload/0/b9/0b94c6b9b73016fa879f3d346f1c0659_thumb.jpg)
,
又∵Rt△AHF∽Rt△ACM,
∴
![](https://img.yulucn.com/upload/7/48/7480e5611d6db47ac273a14f76ba1b24_thumb.jpg)
,∴
![](https://img.yulucn.com/upload/d/c7/dc709f1c93876b54756dc13ccfc214e6_thumb.jpg)
,∴
![](https://img.yulucn.com/upload/6/d2/6d2dcc8bfb4464e07443543a874a6fb8_thumb.jpg)
,
∴
![](https://img.yulucn.com/upload/5/ae/5ae648620f40ccc3c485e56d38fab5b0_thumb.jpg)
=
![](https://img.yulucn.com/upload/f/fd/ffdcc20d54d11fc2fecba34158c68f8a_thumb.jpg)
,
即
![](https://img.yulucn.com/upload/5/2b/52bdec94b0a41078dc5c84fe6eb51255_thumb.jpg)
;
③当8≤t≤12时,如图(3),矩形DEFG与△ABC重叠部分为三角形AGR(当t=12时为一个点),过C作CM⊥AB于M,
则Rt△ARG∽Rt△ACM,
∴
![](https://img.yulucn.com/upload/e/37/e376f919d1e52f68a1252015f2582c52_thumb.jpg)
,∴
![](https://img.yulucn.com/upload/e/61/e61f717acd9cde365bb4e18c147a8f40_thumb.jpg)
,∴
![](https://img.yulucn.com/upload/6/e3/6e3cccc7e68c85cfee1b649dc603a3c8_thumb.jpg)
,
∴
![](https://img.yulucn.com/upload/b/21/b21a830bc8c7b8d04edcfe2f6828cefa_thumb.jpg)
-8t+48。
1年前
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