Answer how you got that "root2" on the eqn.explain detail

It wasn't a good idea starting a new thread to continue asking in the same post. Few would know what you're talking about. I assume you are referring to:

https://www.askmehelpdesk.com/mathematics/directrix-focuses-parabola-216527.html

The formula for the distance from a point to a line is d=\frac{|Ax_{0}+By_{0}+C|}{\sqrt{A^{2}+B^{2}}}

In that event, the \sqrt{2} comes from the coefficients of the line equation you were given.

x-y+5. The coefficients of x and y are 1 and -1, respectively. \sqrt{1^{2}+(-1)^{2}}=\sqrt{2}

See now?

Please, if this has been of help, don't be an ingrate like so many others. Please rate the answer or say thanks.

Hai sir,
Thank you very much for your help.Indians are not like others,we are always greatefull to others who gives us a littie bit of help.
ONce again thanks.we should keep in touch.
Smikesh