電子課本網(wǎng) › 第35頁(yè)

第35頁(yè)

信息發(fā)布者：

???$解：(1)\frac {AB}{BC}=\frac {3}{4}，\frac {CF}{CD}=\frac {4-\frac {7}{4}}{3}=\frac {3}{4}$???

???$(2)因?yàn)閈frac {AB}{BC}=\frac {CF}{CD}=\frac {3}{4}$???

???$所以線段AB，BC，CF，CD成比例$???

???$解：(1)DB=12-AD$???

???$所以\frac {AD}{12-AD}=\frac {AE}{EC}=\frac {6}{4}$???

???$所以AD=\frac {36}{5}$???

???$(2)DB=12-\frac {36}{5}=\frac {24}{5}，AC=6+4=10$???

???$所以\frac {DB}{AB}=\frac {\frac {24}{5}}{12}=\frac {2}{5}$???

???$\frac {EC}{AC}=\frac {4}{10}=\frac {2}{5}$???

???$所以\frac {DB}{AB}=\frac {EC}{AC}$??

?

???$解：設(shè)S_{△COD}= x ， S_{△AOE}=y，$???

???$則\frac {35+x}{30}=\frac {OC}{OF}=\frac {y+84}{40}$???

???$即4x- 3y= 112$???

???$\frac {x}{y+84}=\frac {OD}{OA}=\frac {35}{30+40}$???

???$即2x-y= 84$???

???$解得x= 70，y= 56$???

???$所以S_{△ABC}= 40+ 30+ 35+ 70+84+ 56= 315$???

亚洲激情+欧美激情,无码任你躁久久久久久,我的极品美女老婆,性欧美牲交在线视频,亚洲av高清在线一区二区三区