Thread: Math tricks for everyone View Single Post

 Quote by Robert1986 OK, now I see where you are comming from. IF you are given an equation in this form: ax^2 = bx + c then in some sense your way is easier (though, marginally so, anyone who does a lot of math wouldn't actually move the stuff around as you suggested, they would just know what a, b and c are by looking at the equation) but it requires one to memorize another quadratic formula when the text-book one works just fine given one has enough experience to make simple algebraic manipulations in one's head. But, I assume you would still use the text-book quadratic formula if given this: ax^2 + bx + c = 0, right? Also, did you look what I posted about explaining this more clearly? Did what I write make sense to you, I mean, did my way of getting this result make sense to you? For me, I don't really see a benefit. If you do, that's fine; I don't think you're insane if it helps you. For me, the extra negatives really don't pose much of a problem.
Finally, but it took much more than half an hour LOL. That's because we're not in the same room talking.

I looked at what you wrote and I don't see a problem with it initially, except you put a b^2 where it didn't belong, but that doesn't matter to me because it did not affect your final result.

x = [b' +- sqrt(b'^2 + 4ac')]/[2a] = [(-b)^2 +- sqrt((-b)^2 + 4a(-c))]/[2a]

The rest of it seems fine to me but I must caution you, I am not as rigorous as others. To me, it seems a tiny bit like circular reasoning but I am no expert in logic. Let others more qualified make their assessment of your proof.

I wanted to avoid any connection to the textbook version, that's why i considered the 4 forms, made my arguments, definitions, and derivations.

If i had an equation to solve in the form ax^2 + bx + c = 0 Then I would use the textbook version.

If you gave me 10 equations to solve in the form ax^2 = bx + c then I would feel silly using the textbook version because i know a better version for this form. My version. Imagine... sitting there with pencil and paper, collecting terms on one side, carrying around un-necessary minus signs, transforming subtractions to additions, squaring negatives, on and on, for 10 equations. Or better yet, ask a professional mathematician, who doesn't know, or won't accept my version because it's 'trivial', to do 10 equations by hand, would you chuckle as you watch him struggle?

If you were throwing random forms at me, I wouldn't know what i was going to get next out of possible

form1 ax^2 + bx + c = 0

form2 ax^2 + bx = c

form3 ax^2 + c = bx

form4 ax^2 = bx + c

And you asked me to solve 100 random forms or 1000 or 10^6 random 2nd degree equations, Then I would use my version because I would expect 75% of the forms thrown at me would not be form1

Don't forget that the textbook version has an extra minus sign and subtraction instead of addition. Those 2 differences are going to cause more problems. Does that make sense?