suppose that,we have given following parabolic arc $\sqrt{x}+\sqrt{y}=\sqrt{a}$ we are trying to find shortest distance from origin to this line, i think that if we rewrite it as $\sqrt{y}=\sqrt{a}-\sqrt{x}$, then
$y=a-2\sqrt{ax}-x$ or if we rearrange terms,we get $y+a-\sqrt{ax}-x=0$ distance from origin $(0,0)$ to line $Ax+by+c=0$ is equal $D=(A\cdot0+b\cdot0+c)/(\sqrt{A^2+b^2})$ so in my case what would be minimum distance? please help me