1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

I Another negative one equals one proof

Tags:
  1. Mar 30, 2017 #1
    Hey guys! I need help proving why this proof is wrong. I know it's wrong, but I can't figure out why. Anyway:
    i = sqrt -1
    i^4 = 1
    1^4 = 1
    Substution: i^4 =1^4
    i = 1
    1 = sqrt -1
    1^2 = -1
    1 = 1^2
    1= -1

    If you have any questions, feel free to ask.
     
  2. jcsd
  3. Mar 30, 2017 #2

    mfb

    User Avatar
    2017 Award

    Staff: Mentor

    That step is not valid. Just dropping exponents doesn't even work for real numbers.
     
  4. Mar 30, 2017 #3

    fresh_42

    User Avatar
    2017 Award

    Staff: Mentor

  5. Mar 30, 2017 #4

    Vanadium 50

    User Avatar
    Staff Emeritus
    Science Advisor
    Education Advisor
    2017 Award

    -1^2 = 1^2 therefore -1 = 1. Same idea. Do you see where this fails? No need to drag i into it.
     
  6. Mar 30, 2017 #5
    Yeah, thanks
     
  7. Mar 30, 2017 #6
    4rt them both...
     
  8. Mar 30, 2017 #7

    mfb

    User Avatar
    2017 Award

    Staff: Mentor

    ##(-1)^4 = 1^4##, but obviously ##-1 \neq 1##.
    This is the one-step version of post 1.
     
  9. Mar 30, 2017 #8

    Mark44

    Staff: Mentor

    But -1^2 ≠ 1^2, as I'm sure you know...

    However, (-1)^2 does equal 1^2.
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted



Loading...