数学初三 一道动点题。！ 高分。 直线y=+4/3x+8交x轴于点A,交y轴于点B,
作者&投稿：离珠 （若有异议请与网页底部的电邮联系）
(1) y=-4/3x+8 y=0 联立： A(6,0)
y=-4/3x+8 x=0 联立： B(0,8)
(2) P(6-2t,0) Q(0.6t,8-0.8t)
s=t(8-0.8t)=8t-0.8t^2
当t=5时，△AQP的面积最大。
(3) 0.6t=6-2t
2.6t=6 t=30/13
当t为30/13时,以点A,P,Q为顶点的三角形与△ABQ相似,此时点Q(18/13,80/13)
直线y=-4x/3＋8与x轴,y轴分别交于点A和点B，所以AB两点的坐标是：
A(6,0)，B(0,8)
设M点坐标为（0，y）
则BM=8-y
将△ABM沿AM折叠，点B恰好落在x轴的点B’处，所以B'M=BM=8-y
B'O²=B'M²-OM²=(8-y)²-y²=64-16y
B'O=4√(4-y)
B'A=B'O+OA=4√(4-y)+6
BA²=OA²+OB²=36+64=100
BA=10
B'A=BA
∴4√(4-y)+6=10
√(4-y)=1
4-y=1
y=3
设M点坐标为（0，3）
△AMB的面积=BM*OA/2=(8-3)*6/2=15
因此AC/AQ=AB/AO，其中AC=12，AB=10，AO=6，因此AQ=36/5，因此t=(36/5)/2=18/5(秒)
(2)过Q作QD与x轴垂直，交于D点，作QE与y轴垂直，交于E点
QD/BO=AQ/AB，其中QD=y，BO=8，AQ=2t，AB=10
因此y=8t/5
QE/AO=BQ/AB，其中QE=x，AO=6，BQ=10-2t，AB=10
因此x=(30-6t)/5
(3)若CQ⊥QP，则CD/DQ=DQ/DP
CD=6+x=(60-6t)/5，DQ=y=8t/5，DP=OP-OD=6-t-x=t/5
解得t=6/7
Sweet Home Jiuzhai
From Lanzhou to Jiuzhaigou, bumpy two days. Ali in Tibet hurry over one hundred kilometers a day beginning to show the aftermath. But the first day of Jiuzhai still very disappointed. Maybe I do not like stagnant water and traveling companion, and maybe I feel too deeply in Tibet, Jiuzhaigou and Wucaiche long sea not caused any of my shock, and the mood spread to the companion. This tour the next day after Pearl Beach changed after the third day completely changed our view. Not that Jiuzhai how the United States, but because of Jiuzhaigou is a real paradise.
from the outset, we choose to live in then check wow Village, and because it's clean and not change his mind, whether it is the dead of night or early morning mist is not scattered throughout the two No room for only the owner and us, no one disturb our dreams. Stockade room consists of two parts, the standard brick and wood structure between the common room. Wooden buildings are interesting, but people go on it will make the whole building was shaking, do not think can easily fall asleep. Perhaps because fewer people to stay, wood white linen room, open the window is behind the green mountains. When tourists visit points early in the morning arrived, we're still in bed Dreams of Duke. Get up at eight, ten o'clock, after some dawdling in the courtyard downstairs for breakfast accompanied by the sun, eleven to go out.
Jiuzhai good environmental protection, which is unmatched in Tibet Zada, I used to think there is a real paradise, an oasis in the desert, but where the environment is dirty, but also darker, security is not guaranteed. Jiuzhaigou is just not environmentally friendly green vehicles, choking exhaust, a bit ironic. But managing very well. The first day of play at the ditch, down a plank from the Panda Lake, sunny, we are watching from the leisurely, but did not find the date the ditch in addition to the staff for only two of us. Four weeks silence, a deep shade of the woods began. Avenue quickly back to the woods drilled. More than just five p.m., at the ditch has no people. As we walk in the woods, people outside can not see, so all the shuttle bus was gone. Along the way there cleared personnel on a motorcycle, leave. Seven are living deep in the woods take on board the original staff, we take the car down.
one o'clock the next day just to play Pearl Beach, sun is shining. Jiuzhaigou Valley is surrounded by mountains, not too early too late sun. Just a lot of people. Shiyou could not resist playing the afternoon ran into the woods Shuzheng ditch gone, the results did not dare to go on the sky late backtrack. Walled visit to the tree is a bit hit two Hong Kong friends,herve leger outlet, invited us to drink and chat, feel ten at night, can not find the car to the tree is intended to open a room for one night. Then we ask the driver of a car to take us back, Hunan Province, at the driver immediately and contact Mizoguchi scheduling, but could not hear the answer. When we finished shopping the check he sent us back to wow camp. Jiuzhaigou from his mouth that a good law and order, do not have to worry about security issues, some small animals to guard against is definitely the night after returning home visitors come out to surprise and insisted on inviting us see Zhu toilet. The next day we practice the word, really good.
before going out for the third day is also eleven, the tree channel is very clean, the entire channel to only two of us. Shuzheng road ditch on both sides, but not many people through the woods. We are under the big cliff side of the road through the woods, walking in a circle around the ditch, because hardly any people along the way, so when we break through the trees at the water's edge, suddenly saw a man come out of the time actually scared the daylights. We have arrived back to the original path along the cliff road, but I did not notice too much trance.
live carefree in Jiuzhaigou, no pollution, honest, good management, room and board as long as the money to solve the problem, nothing to worry about. On the third day and really feel I Jiuzhaigou is paradise. But, after all, people are still too many. To Songpan, I began to yearn Kawakita this land.
自己想
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