请教数学句子.

zbdtz88UID??2194239

from ETS: In fact,all positive numbers have two square roots that differ only in sign.
是不是可以理解为,如:根号16等于正负4? 懵了.

HootenannyUID??2216598

理解为：
16=x^2 =>x=±√16=±4

y=√x=x^(1/2)是一个幂函数,对于一个给定的自变量x，只有唯一的y与之对应，即√16＝4