High level mathematics a = 0.9 How to prove that a can be equal to 1a = 0.910a = 9.99a = 9A = 1 before a = 0.9

High level mathematics a = 0.9 How to prove that a can be equal to 1a = 0.910a = 9.99a = 9A = 1 before a = 0.9

Do you want to prove 0.999999 =1?
Proof: let a = 0.999999 (1)
Then 10A = 9.999999 (2)
(2) (1) 9A = 9,
So a = 0.999999 =1.