两根不等长的细线栓在同一点，另一端分别栓两个带同种电荷的小球a，b，电荷量分别是Q₁，Q₂，质量分别是m₁，m₂，当两球处于同一水平面时恰好静止，且α＜β，则造成α，β不相等的原因是（   ）

假定英语课上老师要求同桌之间交换修改作文，请你修改你同桌写的以下作文。作文中共有10处语言错误，每句中最多有两处。每处错误仅涉及一个单词的增加、删除或修改。

增加：在缺词处加一个漏子符号（∧）并在其下面写出该加的词。

删除：在错的词下划一横线，并在该词下面写出修改后的词。

注意：1).每处错误及其修改均仅限一词；

      2).只允许修改10处，多者（从第11处起）不计分。

    Here I will tell you what happened to me the other day. My best friend Alice and I was riding her brother's four-wheeler. She was driving down a road when all of sudden we hit a sand pile and lost control. She was okay and I wasn't. I was knocking unconscious. At first she didn't know how to do but then she heard a truck coming down the road. So she waved down the driver and explain what had happened. The man got out of his truck with a second thought. He rushed over to her and called an ambulance. By that time I was starting to wake up. When I woke up, I saw the man stood over me. I thanked for him. That man was a hero.

解方程：（2x﹣1）²=25．