User:Yath/sandbox1

$x={\sqrt {-N}}$

Failed to parse (SVG (MathML can be enabled via browser plugin): Invalid response ("Math extension cannot connect to Restbase.") from server "http://localhost:6011/en.wikipedia.org/v1/":): {\displaystyle x = \sqrt{y}, \mbox{y \le 0}}

$\mathbb {R} ^{+}$