If $x=9$, then can we write $\sqrt{x}=\pm3$ or only $\sqrt{x}=3$ If $x=9$, then can we write $\sqrt{x}=\pm3$ or only $\sqrt{x}=3$. 
I am confused as square root always gives positive number.
But the irony is that if we have $a^2=9$, then we write $a=\pm3 \text {  where $a=\sqrt{a^2}$ }$

You are right that often $\sqrt{n}$ is meant as the positive root. As a result, it is very common to see the solutions to $x^2=n$ expressed as $x=\pm\sqrt{n}$ rather than $\pm x=\sqrt{n}$. While they are equivalent mathematically, the latte
