在平面直角坐标系xOy中，已知圆M：（x+1）²+y²= $\frac{49}{4}$ 的圆心为M，圆N：（x﹣1）²+y²= $\frac{1}{4}$ 的圆心为N，一动圆与圆M内切，与圆N外切．

（Ⅰ）求动圆圆心P的轨迹方程；

（Ⅱ）过点（1，0）的直线l与曲线P交于A，B两点，若 $\overrightarrow{OA}\cdot \overrightarrow{OB}$ =﹣2，求直线l的方程．

擦去镜头上的灰尘，应使用（　　）

如图所示，当开关S闭合，滑动变阻器的滑片P由右端向左滑向中点处的过程中（   ）

从甲地到乙地，某人步行比乘公交车多用3.6小时，已知步行速度为每小时8千米，公交车的速度为每小时40千米，设甲乙两地相距x千米，则列方程为 ____

    Martin had just finished high school. He would go to college at the far end of the city. He didn't want to live there, and he didn't want to take the bus either. So his father agreed to buy him a car.
    His father spent all his summer teaching him how to drive, from the ABC to the XYZ. Thinking of the great feeling of driving a new car, Martin learned very quickly, and received his driver's license just before his eighteenth birthday.
    The second day, all the family, and their dog, went to a car shop. Martin spent almost all the morning going from one car to another. Finally he saw a red Blue Bird. He had a test drive on the open ground, and called out, “This is what I want, Dad!” When everything was done, they were ready to leave.
    Martin climbed into the front seat. He said excitedly, “It's my first day driving alone. Dad, Mom, and Poo! Enjoy it!”
His dad immediately took the back seat, right behind the new driver. Martin wondered why his father chose that seat, for his father always enjoyed looking in front.
    So he said, smiling, “I'm sure you're back there to have a change after all those weeks of sitting in the front seat teaching me how to drive.”
    “No,” Dad replied, “Do you remember what you did to me all those years when I took you to and from school? I am sitting here to hit and kick the back of your seat all the way!”