足球以1.0m/s的速度水平飞向墙壁,碰到墙壁经0.1s后以1.0m/s的速度沿同一直线反弹回来,足球在与墙壁碰撞过程中 (       )

    Betty started to learn English at the____of six. She went to an after-school English class every week. But Betty thought it was____(bored) to go to her English classes. She didn't think____was important to learn English and she did not need to speak English in her everyday life.

    After she____a school baseball team , she started to know more about the baseball players who joined teams in the USA. Now, she wants to know more about what happens to them. So she reads English newspaper____the Internet. When she meets new words, she looks____up in her dictionary and writes difficult sentences in her notebooks. When she goes to school, she asks her English teacher for____. Little by little, she finds that English is really important, and she is more and more____(interesting) in it.

    Her parents promise to take her to New York to watch a baseball game if she gets good mark in the English exam next month.____exciting it is! Betty is so happy that she works____(hard) on English than before.

沿河县人口大约有66万人，用科学记数法应记为____ 人。

（注：在解题过程中，你也可以阅读后面的材料）

附：阅读材料

   任何一个一元二次方程的根与系数的关系为：两根的和等于一次项系数与二次项系数的比的相反数，两根的积等于常数项与二次项系数的比．

   即：设一元二次方程ax²+bx+c=0的两根为x₁，x₂，

   则：x₁+x₂=﹣ $\frac{b}{a}$ ，x₁•x₂= $\frac{c}{a}$

   能灵活运用这种关系，有时可以使解题更为简单．

   例：不解方程，求方程x²﹣3x=15两根的和与积．

   解：原方程变为：x²﹣3x﹣15=0

∵一元二次方程的根与系数有关系：x₁+x₂=﹣ $\frac{b}{a}$ ，x₁•x₂= $\frac{c}{a}$

∴原方程两根之和=﹣ $\frac{-3}{1}$ =3，两根之积= $\frac{-15}{1}$ =﹣15．