Question

在区间[-1,1]上任取两实数a,b,则一元二次方程x2+2ax+b2=0的两根都为实数的概率为多少？

请求详解，谢谢！

Answer 1

不好意思题目看错了，我以为是2b，原来是b平方，哈哈，那简单多了，不用积分了。。。

Answer 2

4a²-(2b)²>0

|a|>|b|
a为横轴，b为纵轴
就是画十字交叉线，然后落在左右两边区间的概率

十字交叉平分正方形

所以自然是1/2

两根都为实数的概率=1/2

Answer 3

me to her home. Carey is actually not a student, but a manager. She stays in Li's apartment for free， __2___ has to teach Li oral English for 1 hour every day. “She could hardly speak Chinese at the beginning, and __3___ had to guess what each other meant through gestures, ”said Li.
Two months later, they could talk to each oth