X * (X + 1) = Phi

[Deciheximal]

I was curious what the answer to this would be to 10 digits or so. By guess and check, I came to X <= .8668. Is there a better way?

 

[royhaas]

Use the quadratic formula.

 

[Denis]

.8667603991556... or -1.8667603991556...

 

[Deciheximal]

Perfect. Thank you.