if then, iff notation for quadratic equations.

Question

This is correct as far as I know:$$x^2=9 \Leftarrow x=3$$ but :$$x^2=9\Leftrightarrow x=\pm3$$ Is the $\pm $ technically acceptable notation for this relationship to be correct?

Also is it correct to write$$x^2=9\Leftrightarrow x=3,x=-3$$

Answer 1

I'm assuming you're talking in the real numbers:
Firstly yes the $\pm 3$ notation is correct; secondly for your second question you should use "OR" instead of a comma (","); Note that both notations mean the same thing.