J.K Rowling is the writer of the Harry Potter series, the most popular books.

    J.K. Rowling was born in Bristol in 1965. She has one sister 1 is two years younger than her. Both girls loved listening to bedtime 2 . They loved stories about the magical (有魔力的) world. Rowling 3her first story, called rabbit at the age of six.

    4 she graduated from the university, Rowling worked in London. During that time, on a long train trip in the summer of 1990, the idea of a 5 who has magic but doesn't know it himself came to6 . In 1992, Rowling began to teach English. She lived with her daughter, Jessica, and7much time finishing the first Harry Potter book for young8. It came out in 1997. To her 9 , the book was very successful. The film came out in 2001. Now the Harry Potter series is 10with people of all ages.

    Why is the series so successful? Many other magic stories11place in faraway lands in the past or future times,12Harry lives in modern England. He 's also a very normal boy. When other 13 read the story about Harry, they can 14 being like him.

    J.K. Rowling is very happy with her success. She says she will go on 15 children's books.

给出以下问题：

①求面积为1的正三角形的周长；

②求键盘所输入的三个数的算术平均数；

③求键盘所输入的两个数的最小数；

④求函数$f\left(x\right)=\left\{\begin{array}{c}2x,x\ge 3\\ x^2,x<3\end{array}\right.$当自变量取x₀时的函数值．

其中不需要用条件语句来描述算法的问题有____ ．

电流通过一台电动机时产生的热量是1200J，产生的动能是3600J，则电流做功至少为(  )