How do you put 6x2+5y224x+20y+14=0 in standard form, find the center, the endpoints, vertices, the foci and eccentricity?

1 Answer
Mar 15, 2017

Standard forms for the equation of an ellipse are (xh)2a2+(yk)2b2=1 or (yk)2a2+(xh)2b2=1;a>b

Explanation:

Reference for an ellipse
Given: 6x2+5y224x+20y+14=0

Add 6h2+5k214 to both sides of the equation:

6x224x+6h2+5y2+20y+5k2=6h2+5k214

Remove a common factor of 6 from the first 3 terms and a common factor of 5 from the next 3 terms:

6(x24x+h2)+5(y2+4y+k2)=6h2+5k214 [1]

To find the value of h, set the middle term of the right side of the pattern (xh)2=x22hx+h2 equal to the middle term in the first parenthesis in equation [1]:

2hx=4x

h=2

Substitute the left side of the pattern into equation [1]:

6(xh)2+5(y2+4y+k2)=6h2+5k214 [2]

Substitute 2 for h everywhere in equation [2]:

6(x2)2+5(y2+4y+k2)=6(2)2+5k214 [3]

To find the value of k, set the middle term of the right side of the pattern (yk)2=y22ky+k2 equal to the middle term in the second parenthesis in equation [3]:

2ky=4y

k=2

Substitute the left side of the pattern into equation [3]:

6(x2)2+5(yk)2=6(2)2+5k214 [4]

Substitute -2 for k everywhere in equation [4]:

6(x2)2+5(y2)2=6(2)2+5(2)214 [5]

Simplify the right side of equation [5]:

6(x2)2+5(y2)2=30 [6]

Divide both sides of the equation by 30:

(x2)25+(y2)26=1 [7]

Make the denominators squares and swap terms:

(y2)2(6)2+(x2)2(5)2=1 [8]

Equation [8] is the standard form where, h=2,k=2,a=6,andb=5

From the reference:

c=a2b2

c=65

c=1

The center is at (h,k):

(2,2)

The vertices are at #(h, k-a) and (h,k+a):

(2,26)and(2,2+6)

The foci are at: #(h, k-c) and (h,k+c):

(2,21)and(2,2+1)

(2,3)and(2,1)

The co-vertices are at (hb,k)and(h+b,k):

(25,2)and(2+5,2)

The eccentricity is ca=16=66