The letter i is used to signify that a number is an imaginary number. It stand for the square root of negative one. In electrical engineering it is often replaced by the letter j to avoid conflict with the symbol for current. See Imaginary numbers.
i其实就是-1的平方根
然后因为-1的平方根是不存在的嘛，所以他就是imaginary numbers（虚数）
这一题的solution你可以直接写4+根号3 or 4-根号3或者也可以写4±根号3
你是要这个回答吗，不是就吱一声(●'◡'●)
