What Are Quadratic Equation

Solving Quadratic Equations

I'm looking for the equation of a demand curve, which is usually negative sloping, i.e. y = -x. Well, at least that is how it should look. However, I know that y = -x is a linear equation, and that's not exactly what I need. I guess it could be negatively exponential, but I just don't know. Perhaps it might help to give you a few examples of the points on the curve (points are in x:y format)

1) 1,000:400
2) 1,500:300
3) 2,400:200
4) 4,000:100

I should think that the y-intercept would be around 800. It doesn't matter very much whether the curve touches the x-axis, but I would think that the curve would start approaching it around 8,000 or 9,000.

This is actually the curve that I'm trying to find the equation for. Not only that, but then instead of having it in the format of y = ... , I would need it in the format x = ... If you could show me how to find that, I would appreciate it very much.

Answer:

The curve looks like the top right of a circle as I visualise it. You will find it difficult though to work out the exact equation of the curve.

Perhaps this may help put it in the form x=ay^2+bx+c:

y=ax^2+bx+c

y-c=ax^2+bx

You then have to complete the square:

y-c=sq( rt(a)x+(b/(2rt(a)) ) - b^2/4a (test it by multiplying it out. I may have made a mistake)

y-c+b^2/4a= sq( rt(a)x + (b/2rt(a)) )

rt( y-c+b^2/4a ) =rt(a)x + (b/2rt(a))

rt( y-c+b^2/4a)- (b/2rt(a)) = rt(a)x

<rt( y-c+b^2/4a ) - (b/2rt(a)) >/ <rt(a)>= x

A bit difficult to follow, so suggest writing it out on paper. Have used sq to mean ^2 at times and obviously rt(x) to mean the square-root of x. May be some mistakes here so apologise in advance if so, but gives the general idea on how to isolate x

The test results are in and staff writer Kristen Cates won't be ... - Great Falls Tribune

The test results are in and staff writer Kristen Cates won't be ... Great Falls Tribune, MT - Jun 30, 2008 Talk to me about quadratic equations, and I run the other direction. However, in my reporting days I've boosted my skills by calculating and analyzing Excel ...

How maths can be fun - Norfolk Eastern Daily Press

How maths can be fun Norfolk Eastern Daily Press, UK - Jun 19, 2008 Meanwhile, at high schools, recruitment of maths teachers is becoming as difficult as a quadratic equation. One theory about why maths no longer adds up for ...

Plainfield High School awards diplomas: Help when you can, grads urged - Norwich Bulletin

Plainfield High School awards diplomas: Help when you can, grads urged Norwich Bulletin, CT - Jun 19, 2008 "You may never remember the quadratic equation or the principles of genetics after your final exams," he said. "But please remember the principal lessons ...

Roadrunner: It's way more than just a 'bee-beep' birdie - El Paso Times

Roadrunner: It's way more than just a 'bee-beep' birdie El Paso Times, TX - Jun 20, 2008 A mind-boggling calculation is a quadratic equation. And Roadrunner can do 1000 trillion of those a second? I doubt it. OK, just for the sake of argument, ...

Derbyshire: June Diary - National Review Online Blogs

Derbyshire: June Diary National Review Online Blogs, NY - Jul 1, 2008 You want to understand quadratic equations? Solve a couple hundred of them, by all the different methods — graphical, formulaic, sight-factorization, ...

Lisa Ryckman on abs workouts - Rocky Mountain News

Lisa Ryckman on abs workouts Rocky Mountain News, CO - Jul 1, 2008 Remember your quadratic equations: what you do to one side, you must do to the other. Mark_Wolf(Q) If you have a back problem - or want to avoid one - what ...

Math whiz eases onto the fast track - Baltimore Sun

Math whiz eases onto the fast track Baltimore Sun, United States - Jun 8, 2008 "Do you know what the quadratic equation is?" Benjamin asked. She stared back blankly. "Don't worry about it. You'll learn about it later," he said. ...

RHAM Graduates Receive Diplomas, Advice - Hartford Courant

RHAM Graduates Receive Diplomas, Advice Hartford Courant, United States - Jun 20, 2008 ... that he no longer works at RHAM, he can answer some of their most-asked questions — and no, they would never need to use the quadratic equation again. ...

The Derivation of "Logistic-shaped" Discovery - The Oil Drum

The Derivation of "Logistic-shaped" Discovery The Oil Drum - Jun 26, 2008 The post addresses the origins and relevance (or lack thereof) of the logistic equation as it is commonly used in projecting/modeling oil production ...