
PreCalculus PreCalculus Math Forum 
 LinkBack  Thread Tools  Display Modes 
August 26th, 2017, 08:47 PM  #1 
Newbie Joined: Aug 2017 From: USA Posts: 1 Thanks: 0  The equation of all parabolas given a vertex and a point
"Find the equation of all parabolas having vertex (2, 3), passing through (2, 1), and whose directrix is horizontal or vertical." How do you find the one equation that would satisfy the given information? My method of solving left me with 2 equations (one for each of the vertical and horizontal directrix). 
August 26th, 2017, 11:42 PM  #2 
Senior Member Joined: Sep 2015 From: Southern California, USA Posts: 1,410 Thanks: 715 
I can't see how you would have the same equation for both orientations of the parabola. One would be quadratic in $x$ the other would be quadratic in $y$ 
August 27th, 2017, 04:17 AM  #3 
Math Team Joined: Jan 2015 From: Alabama Posts: 2,647 Thanks: 680 
A vertical parabola is a function of x but not y. A horizontal parabola is a function of y but not x. There cannot be a formula in x and y only that gives both.


Tags 
equation, parabolas, point, vertex 
Thread Tools  
Display Modes  

Similar Threads  
Thread  Thread Starter  Forum  Replies  Last Post 
find the equation for a parabola whose vertex is....  GIjoefan1976  Algebra  3  June 2nd, 2017 02:41 PM 
Determine the equation of a quadratic function that has it's vertex ....  GIjoefan1976  Algebra  7  April 28th, 2017 04:17 AM 
Parabola, tangent point&line, the vertex and 8(?!)  elim  Geometry  5  September 19th, 2014 02:11 PM 
Parabolas and turning point  sallyyy  Algebra  6  November 14th, 2010 12:24 PM 
Find equation of the common tangent to the parabolas  varunnayudu  Trigonometry  3  December 1st, 2009 10:13 PM 