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We did in school, but the original equation x^2 + bx + c was rewritten as x^2 + bx + (b/2)^2 - (b/2)^2 + c, and now you see the binomial. Our teacher said it fe
by HarryHirsch 5y ago
We did in school, but the original equation x^2 + bx + c was rewritten as x^2 + bx + (b/2)^2 - (b/2)^2 + c, and now you see the binomial. Our teacher said it felt like pulling a rabbit out of the hat.
- ogogmad 5y agoWhere did you go to school? I'm from the UK. > Our teacher said it felt like pulling a rabbit out of the hat. This is something you do when you prove something. It's the shortest way but it's also totally lacking in motivation. It's a Deus Ex Machina, which is a terrible way of explaining mathematics to people. When I was taught "completing the square", it was presented as another method for solving a quadratic equation, and not just a proof of the quadratic formula. If people in the US are taught this way, that's not good for US-ians. And this whole discussion is weirdly US-centric.
- HarryHirsch 5y agoThis was in Germany, in 9th grade. Should have added that this was the proof of the quadratic formula.