Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

I Proof: 0.9999 does not equal 1

  1. Nov 22, 2017 #1
    Or rather counter proof.
    They said x=0.999...
    but this is obviously wrong, you can't substract infinity from infinity unless you consider infinity a number and if so then you would get 8.99...1 and not 9. either way 0.999....= 1 is wrong. and is not different than saying (0.999...) +x=1.99...8 you can't add an infine amount of nines to an infinite amount of nines or subtract. if you could then you would consider infinity as a number and in that case the proof is also wrong
  2. jcsd
  3. Nov 22, 2017 #2


    User Avatar

    Staff: Mentor

    This subject has been discussed many times on PhysicsForums. Please do a search of the forum or look at the "Similar Discussions" links below.

    Yes, 0.999... = 1.

    Thread closed.
  4. Nov 22, 2017 #3


    Staff: Mentor

    We are not subtracting infinity from infinity here. The subtraction is 9.999... - 0.999..., with each number having an infinte number of 9 digits to the right of the decimal point. The result is 9.000..., with an infinite number of 0 digits to the right of the decimal point.
    As DrClaude said, this has been discussed many times here at PF.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook