Technically, all numbers have two square roots, one positive and the other negative, since squaring the negative number results in a positive number. Thus, sqr(9)=plus or minus 3, written +/-3; likewise <math>\sqrt{-9} = \pm3i</math>. | Technically, all numbers have two square roots, one positive and the other negative, since squaring the negative number results in a positive number. Thus, sqr(9)=plus or minus 3, written +/-3; likewise <math>\sqrt{-9} = \pm3i</math>. |