   Def of Quadratic Equation.
  The definition I''m given of a quadratic equation is an expression, equation, or function that involve sums of constants and first and second powers of variables and no higher powers.  So in symbol terms (a+b)^2 is pretty much what is being described right here.  But, question #1 is: Which is not a quadratic equation?(a) y=(1/2)x^2 (b) xy=4 (c) x^2 + y^2 =10 (d) y=2xI''m guessing the answer is (d).  But then, what about b?   Charles Hwang    -aka Tazel[Maxedge My Site(UC)|E-mail|NeXe|NeHe|SDL][Google|Dev-C++|GDArticles|C++.com|MSDN]    
  I don''t see how b,c, or d count as quadratic.When b is graphed it will look nothing like a parabola. In fact, its value is undefined at zero, and drops sharply as x increases.c is the formula of a circle.d is just a line ;  both b and d are not quadratic equations. b is hyperbole if i got the terminology right and d is a linear equation. ;  According to <a href = "http://mathworld.wolfram.com/QuadraticEquation.html">mathworld</a>. A quadratic equation is defined as: A quadratic equation is a second-order polynomial equation in a single variable x.Therefore I would say (a) is the only one that IS a quadratic. ;  Quadratic equations must have powers of 2, but no higher.  So b shouldn''t actually be a quadratic equation, unless x=y.  Definitely go with d, though, as linear equations are definitely not quadratic.   ;quote:Original post by Eelco  both b and d are not quadratic equations. b is hyperbole if i got the terminology right and d is a linear equation.   Its spelled hyperbola.a hyperbola takes the form a^2/x^2 - b^2/y^2 = 1 ;quote:Original post by cowsarenotevil  Quadratic equations must have powers of 2, but no higher.  So b shouldn''t actually be a quadratic equation, unless x=y.  Definitely go with d, though, as linear equations are definitely not quadratic.    your opinion is wrong! ;quote:Original post by Anonymous Poster  According to &lt;a href = &quot;http://mathworld.wolfram.com/QuadraticEquation.html&quot;&gt;mathworld&lt;/a&gt;. A quadratic equation is defined as: A quadratic equation is a second-order polynomial equation in a single variable x.Therefore I would say (a) is the only one that IS a quadratic.   Actually, that would mean none of them is a quadratic equation, unless y is taken to be a constant, in which case a and c is quadratic. ;quote:Original post by Nervo  your opinion is wrong!   You''re right, it is.  I forgot that the x and y in b were actually representative of X and Y.   ;  Closing the thread. Review Forum FAQ regarding the policy on homework or homework-like questions, .   Graham RhodesSenior ScientistApplied Research Associates, Inc. 