自我介紹英語小短文 內容是：我的名字是***，今年14歲，在應行久外語實驗上學，學號是47。我的興趣愛好是打羽毛球，我喜歡的顏色是藍色、黑色。

自我介紹英語小短文 內容是：我的名字是***，今年14歲，在應行久外語實驗上學，學號是47。我的興趣愛好是打羽毛球，我喜歡的顏色是藍色、黑色。

hello everyone！my name is**.i'm fourteen years old this year，i study in yingxingjiu foreigh languageschool.mystudent number is 47.i have lot's of hobbies，and i like play badminton verywell.bythe w…

一篇關於中國人口問題的英語文章，急用！差不多70個詞左右~時間緊迫，
要是70個單詞左右的，不要多了~

Regional Adjustment Permitted to Solve Population Problem
The population structural contradiction in China is growing with every passing day and the next 15 years will be crucial for China to tackle this problem. The population policies in China will remain unchanged and there will be only some supplement and improvement that allows the regional readjustment to solve the problems，says the Legal Daily.
The“One-child policy”China adopted in the late 1970s and the early 1980s has effectively controlled nation's total population and reduced newborn babies by 300 million. The childbirth level has dropped to that of the developed countries. Consequently，the problems such as the gender disproportion of newborn babies and aging emerged.
The gender disproportion of newborn babies began to rise from the middle of 1980s. The number climbed from 108.47 in 1980 to 116.92 in 2000，i.e. nearly 117 boys were born as against an average of 100 girls，which largely deviated from the normal range of 103 to 107.
The population structural contradiction is also illustrated by the growing aging process. Currently，there are 88 million senile citizens over 65 years of age，which takes up 7 percent of the total national population. It is estimated that the aged population above 65 will make up 11.8 percent of the nation's total by 2020，and 25 percent by the mid 21 century.
The emergence of the population structural contradiction changed the regional childbirth policy. It is reported that Shanghai municipal government has abolished the double material rewards to the couple who does not bear child and ease the conditions for the one who wants to have a second child.
Yu，Xuejun，director of the Policy and Regulations Department of National Population and Family Planning Commission，said the change Shanghai has made is a regional readjustment and within the nation's general population policies. It does not overrun the national principle，the basic“one-child policy”for family planning.
The next 15 years starting from now will be the crucial period for China's population development，pointed out Yu Xuejun. All the negative influences foreseen and unforeseen when stipulating“one-child policy”will come to appear. In this 15-year-long crucial period，China's population will remain unchanged and there will be only some supplement and improvement. China's population will climb to its peak of 1.6 billion by 2055. But if every couple has a second child，that peak will arrive 10 years earlier. As long as we maintain the current childbirth rate，the nation's total population will be kept within 1.5billion by 2035.

一個長方形，長新增4分之1，寬新增5分之1，如果面積新增20平方釐米，那麼原來長方形的面積是（）平方釐米

原來長方形的面積是（40）平方釐米
假設長x寬y
新增後的面積就是
（x+x/4）（y+y/5）
=3xy/2
3xy/2-xy=20
所以xy=40

已知直線y=3/2x-4與y=-4/3x+k/3的交點在第四象限，求K的取值範圍
要詳解……過程……說明……

根據題意，
3/2X-4=-4/3X+K/3
解得X=24/17 + 2K/17
把X=24/17 + 2K/17代入y=3/2x-4
解得Y=3K/17 - 32/17
因為Y＜0 X＞0
所以（3K/17 - 32/17）＜0
（24/17 + 2K/17）＞0
解得-12＜K＜32/3

f（x）=X-1/x+1的導數是什麼分數的求導公式是什麼

1+1/（x的平方+2x+1）

兩個正方形有一部分重疊在一起.甲正方形中重疊部分與陰影部分的面積比是3:13，乙正方形中重疊部分與陰影部分的面積比是1:2.求甲正方形與乙正方形的面積比.

甲正方形的面積×33+13=乙正方形的面積×11+2甲正方形的面積：乙正方形的面積=13:316=16:9答：甲正方形與乙正方形的面積比是16:9.

已知f x是二次函數，若f（0）=0且f（x+1）=f（x）+x+1，則f（X）的運算式為

f（x）是二次函數，設f（x）=ax^2+bx+c.根據f（x+1）=f（x）+x+1，f（0）=0有：令x+1=0，則x=-1，有f（0）=f（-1）+（-1）+1=f（-1），既f（-1）=0；令x=0，則有f（1）＝f（0）+0+1，即f（1）=1將f（-1），f（0），f（1）代入f（x）有：a-b+c＝0c＝0a+b+c＝1解…

k取______時，二次三項式4x2-kx+3是一個完全平管道.

∵-kx=±2x×3，∴k=±43.

為什麼a3+a4+a5=（a2+a3+a4）•；q？

an是等比數列吧？等比數列中，an=a（n-1）*q，所以a3=a2*q，a4=a3*q，a5=a4*q，兩邊加起來就得到你的那個等式了.

如圖，點D是Rt△ABC的斜邊AB上的一點，DE⊥BC於E，DF⊥AC於F，若AF=15，BE=10，則四邊形DECF的面積是______.

∵DF⊥AC，DE⊥BC，∴∠DFC=∠C=∠DEC=90°，∴四邊形DFCE是矩形，易知DF‖BC，則∠ADF=∠B，又∵∠AFD=∠DEB，∴△ADF∽△DBE，∴DFBE＝AFDE，即DE•DF=AF•BE=150，∴S矩形DFCE=DE•DF=150，即四邊形DFCE的面積為150.