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You are not logged in. #1 20121202 16:49:26
Deriving the quadratic formula questionI have only one question for this. What I want to know is how the common denominator for c/a is gotten. I thought I had figured it out, but I'm pretty sure I was on the far side of mars in relation to how close I actually was to figuring it out. I THOUGHT, that since a variable with no coefficient has an implied value of 1, that I could turn c/a into c/2a that way, therefore gaining the ability to get the common denominator of 4a. This is wrong though I'm pretty sure. I'm out of ideas at the moment. I need to step away from this and think some more . I would appreciate if someone could explain the process of how c/a gets the common denominator of 4a. #2 20121202 18:40:36
Re: Deriving the quadratic formula questionRead this Last edited by debjit625 (20121202 18:41:36) Debjit Roy ___________________________________________________ The essence of mathematics lies in its freedom  Georg Cantor #3 20121202 20:11:09
Re: Deriving the quadratic formula questionhi geramul You cannot teach a man anything; you can only help him find it within himself..........Galileo Galilei #4 20121202 21:38:50
Re: Deriving the quadratic formula questionThanks guys. I was learning to do this through a different slightly different method however, and even though this method looks a bit shorter I'd prefer to stick with what I'm already familiar with . If you could explain how c/a gets the common denominator of 4a in my version of the problem bob that'd be great . #5 20121203 00:44:45
Re: Deriving the quadratic formula questionhi geramul, You cannot teach a man anything; you can only help him find it within himself..........Galileo Galilei #6 20121203 10:07:59
Re: Deriving the quadratic formula questionAlright let me start from the beginning. What I do here first is I move the "loose" number over to right. Now we have Now I take the coefficient on and divide it through the entire equation. Now my method tells me that I take half of the middle term, square it and then add it to both sides. We end up with this. This is where I got stuck. I don't know how to get the common denominator of 4a for c/a. I hope I wrote everything out correctly as I was doing this through memory, and keeping track of exponents and what not can be a little tough when typing it out lol. #7 20121203 10:52:36
Re: Deriving the quadratic formula questionOK, so carrying on from there: Then put all over this denominator and rearrange. Then you can square root everything. Only one +/ sign is needed in the final expression. Take the b/2a term across to the right hand side, all over the same denominator. Hopefully that sorts it out for you. Bob You cannot teach a man anything; you can only help him find it within himself..........Galileo Galilei #8 20121203 14:45:12
Re: Deriving the quadratic formula questionI actually watched a video that explained it that way. I'm still confused on one thing though, I want to know where the 4a that we multiply c/a comes from. That's what I'm trying to figure out. The 4a we multiply against c/a can't just come from nowhere right? Nothing in math can just come from "thin air" right? I mean we can't just say "We're going to multiply c/a by 4a just because", that 4a has to come from some process and that's what I want to know. #9 20121203 15:30:49
Re: Deriving the quadratic formula questionYout aren't multiplying by 4A but rather multiply by 4A / 4A. Which is the same as multiplying by 1. #10 20121203 16:05:49
Re: Deriving the quadratic formula questionAh, so let me try something here. #11 20121203 19:32:25
Re: Deriving the quadratic formula questionhi geramul
Ok, don't worry. I'll try to sort that out. It is an algbra misunderstanding. When I have trouble with algebra, I go back to some numbers and try the same thing. Let's say that c = 3, b = 12 and a = 5 Now, if you have two fractions to add together, you have to make the denominators the same. I want both /100 So multiply the fraction by 4 x 5 Now with letters Bob You cannot teach a man anything; you can only help him find it within himself..........Galileo Galilei #12 20121204 08:32:02
Re: Deriving the quadratic formula questionAh I'm sorry bob, but I don't think you're getting what I'm trying to say. I think I have a better way to explain it, check this out. Last edited by geramul (20121204 08:40:38) #13 20121204 08:34:48
Re: Deriving the quadratic formula questionWhy nog justmultiply the top and the bottom of the fraction by 4 like Bob said? The limit operator is just an excuse for doing something you know you can't. “It's the subject that nobody knows anything about that we can all talk about!” ― Richard Feynman “Taking a new step, uttering a new word, is what people fear most.” ― Fyodor Dostoyevsky, Crime and Punishment #15 20121204 08:47:20
Re: Deriving the quadratic formula questionWell you could multiply by 7/7 or xyz/xyz or 4pq/4pq You cannot teach a man anything; you can only help him find it within himself..........Galileo Galilei #17 20121204 09:12:53
Re: Deriving the quadratic formula questionFollow this link and learn how to complete the square. You cannot teach a man anything; you can only help him find it within himself..........Galileo Galilei 