解下列方程（1）x（2x+3）=4x+6 （2）x2-2x-399=0．_爱下问搜题

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问题解答题

解下列方程

（1）x（2x+3）=4x+6

（2）x²-2x-399=0．

答案

（1）x（2x+3）=4x+6，

变形得：x（2x+3）=2（2x+3），

移项得：x（2x+3）-2（2x+3）=0，

因式分解得：（x-2）（2x+3）=0，

可得：x-2=0或2x+3=0，

解得：x₁=2，x₂=-

3

2

；

（2）x²-2x-399=0，

移项得：x²-2x=399，

配方得：x²-2x+1=400，即（x-1）²=400，

开方得：x-1=20或x-1=-20，

解得：x₁=21，x₂=-19．

单项选择题

丹毒发于小腿，称为（）

A.流火

B.抱头火丹

C.内发丹毒

D.赤游丹

E.流注

完形填空

Good afternoon, everyone,
I’d like to introduce my friend Christy to you all. Christy is a great example of how one person with 1   can make her dream a reality, so she should win the Student of the Year Award.
Christy loves to ride bikes. She does not just ride along city streets, 2   . She is interested in 3    trail (小路) rides. 4    Christy knew that people who love riding had to travel 5   the city to locate good bike trails, so she 6   to do something.
Christy knew that Roosevelt Park had a clean, lively creek（小溪）7   through it. 12 miles of land around the creek was 8   used. Christy decided to get together with other trail9  to ask the city council to 10  a bike path along the unused land. Christy   11 a petition (请愿书). She and other riders asked all of their biking friends if they would12   the list, and they gathered 300 signatures. The city council evaluated the 13   and, more 14  , agreed to allow the bike trail.
The 15   took two months of work, and now Roosevelt Park has a 16   bike trail. It has many ups and downs; it is a great ride. This trail is becoming one of the community’s important 17   spots. I can’t 18   with Christy when we ride together, but I am glad that she decided to work hard to begin the 19     of the Roosevelt Park bike path. Christy 20   this award because she acted on her dream, causing a community to come together.
Thank you!

B．satisfaction

C．determination

A．importantly

D．necessarily

A．destruction

B．organization

C．construction

A．interesting