sign up I login
 advanced
refer a friend - earn nickels!!

Ask & Discuss Questions with Community & Experts

Moderation Team
 90 chars left    advanced
Ask iit jee aieee pet cbse icse state board community Community Discussion Question: Parabola
Forum Index -> Analytical Geometry like the article? email it to a friend.  
Author Message
heavensablaze (106)

Cool goIITian

Olaaa!! Perrrfect answer. 18  [26 rates]

heavensablaze's Avatar

total posts: 84    
offline Offline

Find the equation of the parabola whose axis parallel to y-axis and which passes through the points (1,0) , (0,0)


 


and (-2,4) .


Rates assured

    
allamraju (3422)

Blazing goIITian

Olaaa!! Perrrfect answer. 606  [802 rates]

allamraju's Avatar

total posts: 1014    
offline Offline

The eqn. of the parabola is (x-1/2)2=(3/2)(y+1/6).


Since the axes is parallel to Y-axis,It's eqn. is of the form


(x-h)2=4a(y-k).Now,Substitute the given points in the eqn. to find a,h,k.


h2=-4ak  ,  (h-1)2=-4ak  ,  (h+2)2=4a(4-k)


Subtracting 1 from 2,we get,h=1/2.So,ak=-1/16 and a(4-k)=25/16


Dividing these two,we get,k=-1/6 and hence,a=3/8.


Thus,the eqn. is (x-1/2)2=(3/2)(y+1/6).


On simplifying,it becomes 2x2-2x-3y=0.


MAKING A MISTAKE IS HUMAN BUT REPEATING IT IS IDIOTIC.
 this reply: 2 points  (with Olaaa!! Perrrfect answer.   in 1 votes )   [?]
 
You have to be logged on to rate
  
karansingh (401)

Blazing goIITian

Olaaa!! Perrrfect answer. 73  [91 rates]

karansingh's Avatar

total posts: 375    
offline Offline

General form of Parabola with Axis parallel to y axis: (x-a)2 = 4k(y-b)


From (0,0), we have a= -4kb                                                             ----------------------------         A


From (1,0), we have 1+a2-2a = -4kb                                                    ------------------------------      B


From (-2,4), we have 4+a2+4a = 16k - 4kb                                        --------------------------------       C


From A and B,  1-2a = 0, so a = 1/2.


From C and A, 4+4a=16k or 1+a=4k or k=1/4 + a/4 = 3/8. so k = 3/8.


From A, 1/4 = -3b/2  or b = -1/6.


So equation of the parabola is (x - 1/2)2 = 4 * (3/8) * (y + 1/6).


 


RATE ME IF I AM CORRECT

 this reply: 2 points  (with Olaaa!! Perrrfect answer.   in 1 votes )   [?]
 
You have to be logged on to rate
  
 
Forum Index -> Analytical Geometry
Go to:   

Top Offers for goIITians
Correspondence Courses
Brilliant Tutorials
Narayana Institute
Aakash Institute
Classroom/Crash Courses
Narayana - Kota , Delhi , Others
Brilliant Tutorials - Class , Crash
Aakash Institute - Medical , Engg
Online Test Series
Brilliant Tutorials
Narayana Institute
Aakash Institute
Mahesh Tutorials
AMITY      Sri Chaitanya