水仙花又称凌波仙子，在中国已有一千多年栽培历史，为中国传统名花之一．某探究小组为了探究“环境条件对水仙花开花时间的影响”，他们选取品种、成熟度和大小等相同的三个具备开花能力的水仙花鳞茎，分为甲、乙、丙三组，同时置于如表所示的环境中进行培养，观察并记录从开始培养到第一朵花开放的时间．

请分析回答：

对于函数f（x），若存在x₀∈R，使f（x₀）=x₀成立，则称x₀为f（x）的一个不动点．设函数f（x）=ax²+bx+1（a＞0）．

（Ⅰ）当a=2，b=﹣2时，求f（x）的不动点；

（Ⅱ）若f（x）有两个相异的不动点x₁，x₂，

（ⅰ）当x₁＜1＜x₂时，设f（x）的对称轴为直线x=m，求证：m＞$\frac{1}{2}$；

（ⅱ）若|x₁|＜2且|x₁﹣x₂|=2，求实数b的取值范围．

阅读理解

　　 Jeff Keith has only one leg. When he was 12 years old, Jeff had cancer. Doctors had to cut off most of his right leg.

       Every day Jeff puts on an artificial leg. With the plastic artificial leg, Jeff can ride a bicycle, swim, and play soccer. He can also run.

Jeff made a plan with his friends who had plastic legs, too. They decided to run across America.

      When he was 22 years old, Jeff Keith ran across the United States from the east to the west. He started running in Boston. Seven months later, he stopped running in Los Angeles. He ran 3, 200 miles. Jeff stopped in cities on the way to Los Angeles. In every city people gave Jeff money. The money was not for Jeff, but for the American Cancer Society.

        Jeff is disabled, but he can do many things. He is studying to be a lawyer. Jeff says, “People can do anything they want to do. I want people to know that I ran not only for disabled people, I ran for everybody. ”

如图所示，重为8N的石块浸没在水中称重时为5N，则石块受到的浮力大小为（　　）