在横线内填入合适的数。

470－____＝420   200＋____＝280  ____＋2500＝2800  ____＋520＝820

对于二次函数y=x²-2mx-3，有下列说法：

①它的图象与x轴有两个公共点；

②如果当x≤1时y随x的增大而减小，则m=1；

③如果将它的图象向左平移3个单位后过原点，则m=-1；

④如果当x=4时的函数值与x=2008时的函数值相等，则当x=2012时的函数值为-3．

其中正确的说法是____．（把你认为正确说法的序号都填上）

   Steven Jobs, the designer of Apple Computer, was not clever when he was in school. At that time, he was not a good student and he always made troubles with his schoolmates. When he went into college, he didn't change a lot. Then he dropped out（退学）. But he was full of new ideas.
   After he left college, Steven Jobs worked as a video game designer. He worked there for only several months and then he went to India. He hoped that the trip would give him some new ideas and give him a change in life. Steven Jobs lived on a farm in California for a year after he returned from India.
   In 1975, he began to make a new type of computer. He designed the Apple Computer with his friend in his garage (汽车库). He chose the name "Apple" just because it could help him to remember a happy summer he once spent in an apple tree garden. His Apple Computer was such a great success that Steven Jobs soon became famous all over the world.

在平面直角坐标系中，下面的点在第一象限的是（ ）