实数情况的开平方(本文简称开方),大家十分熟悉:设a是正实数,开方的本质是求方程y2=a的根,即求一个实数y,使它的平方等于a.问题是满足y2=a的根有二个,22=4.(-2)2=4.因此正数开平方有二个根,y1=2,y2=-2我们称其中取正实数的一个为正根,或算术 The real number of open square (this article referred to as the square root), we are very familiar: Let a be a positive real number, the essence of the square is to find the root of the equation y2 = a, that is, to find a real number y, so that its square is equal to a. The problem is to satisfy There are two roots in y2 = a, 22 = 4. (- 2) 2 = 4. Therefore, there are two roots in the positive open square, y1 = 2 and y2 = -2. We call them positive roots , Or arithmetic