I am a high school student in the UK and have a mathematical problem i cannot get my head around.

It has been explained to me that 0.999... recurring equals 1.

It has also been explained that the gradient on a parabola will never be vertical.

If 0.999... can 'touch' 1 and equal 1

and the gradient of a parabola will get closer and closer to being vertical but never vertical

Is there a relationship between a decimal that gets closer and closer to 1, in that 0.999 is closer to 1 than 0.9 and that a parabola's gradient gets closer and closer to vertical?

And if 0.999.. recurring can equal 1 then why can't a parabola's gradient also be vertical?

Say you had the line y=0.999 and the y intercept is 0.999.

If you had the line y=0.999... recurring, the y intercept would be 0.999... recurring. So if you zoomed in and zoomed in on the graph, the y intercept would never be 1?

Thanks