dsgrue3 said:
x = 2 cannot ever be -2, it will always be 2 and no other value. It has already been declared as such. You're abusing the word "or" here which actually not mean what you're saying. It is really an "either" rather than an "or." "or" as you imply is intended to be an exlusive or. It isn't in this case as both solutions are proper. |
Of course x will never be equal to 2. But, mathematical logic use the word "or" in the very manner I used it. If you alone give it another meaning, you won't make it to the right conclusion.
First of all, your computations are meaningless in a mathematical point of view. You should've write
x=2 => x²=4 => (x=2 or x=-2).
In this case, there is no mathematical flaw and everything is correct: the "or" has to be understood in a mathematical way, i.e. the assertion is true if and only if x is equal to one of the answers.
If I say that you're alive or you're dead, is that sentence right or not?
It reminds me an old joke about a logician who just had a baby. One of his/her friend calls him and ask "Is it a he or a she?" and the logician just answers "Yes". And from a logical point of view, he's true.
