Soleron on 30 April 2013
| dsgrue3 said: x = 2 x^2 = 4 x = +/- 2 Fuzzy math is fuzzy. This is why it doesn't sit well with me. I understand it through Pezus' example with fractions, but this isn't an equation. It's just an assertion. It isn't a proof at all. Surely you admit -2 != 2? |
you're not allowed to multiply or divide equations by x without handling the fact you just added/removed a solution. In this case the second negative solution is an artifact because you multiplied by x. This happens all the time in real physics problems and you can just ignore the other solution. There is a more formal way to deal with it in pure maths but I'm not practiced with it.
