I do understand this:

nguyendinhtuong wrote:

You could see that the value is getting nearer to 3

Is this some kind of rule or something? :

Bunuel wrote:

\(x=\sqrt{6+({\sqrt{6+\sqrt{6+\sqrt{6+...})}}}}\), as the expression under the square root extends infinitely then expression in brackets would equal to \(x\) itself and we can safely replace it with \(x\)