SOLUTION: how can I solve this use the eccentricity of each hyperbola to find its equation in standard form center(4,1),horizontal transverse axis is 12 and eccentricity 4/3

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Question 717075: how can I solve this use the eccentricity of each hyperbola to find its equation in standard form center(4,1),horizontal transverse axis is 12 and eccentricity 4/3
Found 2 solutions by KMST, Edwin McCravy:
Answer by KMST(5328) About Me  (Show Source):
You can put this solution on YOUR website!
The equation of a hyperbola with a horizontal transverse axis can be written in the form
%28x-h%29%5E2%2Fa%5E2-%28y-k%29%5E2%2Fb%5E2=1
I had to look it up (not good with names), but that is what is called the standard form.
(h,k) is the center
Center, vertices, and foci are on the horizontal line y=k
For the vertices,
%28x-h%29%5E2%2Fa%5E2=1 --> %28x-h%29%5E2=a%5E2 --> abs%28x-h%29=a
They are at distance a from the center, on line y=k
and 2a is the distance between the vertices.
The segment (and the distance) between the vertices is called the transverse axis.

So far we know
h=4, k=1, and 2a=12 --> a=6

The eccentricity e is defined based of the focal distance c
(distance from each focus to the center) as
e=c%2Fa
and it turns out that a, b and c are related by c%5E2=a%5E2%2Bb%5E2
We know e=4%2F3 so
4%2F3=c%2F6 --> c=6%2A4%2F3 --> c=8
Then, plugging that (along with a=6) into c%5E2=a%5E2%2Bb%5E2 we get
8%5E2=6%5E2%2Bb%5E2 --> 64=36%2Bb%5E2 --> b%5E2=64-36 --> b%5E2=28

Finally, plugging the values given (or very easily found) for a, h, and k, plus the hard earned value for b%5E2 into the standard form we get
highlight%28%28x-4%29%5E2%2F36-%28y-1%29%5E2%2F28=1%29

Answer by Edwin McCravy(20059) About Me  (Show Source):
You can put this solution on YOUR website!
how can I solve this use the eccentricity of each hyperbola to find its equation in standard form center(4,1),horizontal transverse axis is 12 and eccentricity 4/3.
You need to know 5 things about hyperbolas to solve this problem:

1. The equation of a hyperbola with horizontal transverse axis is 
%28x-h%29%5E2%2Fa%5E2%22%22-%22%22%28y-k%29%5E2%2Fb%5E2%22%22=%22%221

2. The length of the transverse axis is 2a, 

3. The eccentricity is c%2Fa,

4. The center is %22%28h%2Ck%29%22

5. c%5E2%22%22=%22%22a%5E2%2Bb%5E2

center(4,1) 

That tells us that h = 4 and k = 1

horizontal transverse axis is 12

That tells us that 2a = 12
                    a = 6

eccentricity 4/3

That tells us that   c%2Fa+=+4%2F3

Substituting a = 6,  c%2F6+=+4%2F3
Cross multiplying,   3c+=+24
                     +c+=+8

c%5E2%22%22=%22%22a%5E2%2Bb%5E2
8%5E2%22%22=%22%226%5E2%2Bb%5E2
64%22%22=%22%2236%2Bb%5E2
28%22%22=%22%22b%5E2

So

%28x-h%29%5E2%2Fa%5E2%22%22-%22%22%28y-k%29%5E2%2Fb%5E2%22%22=%22%221

becomes:

%28x-4%29%5E2%2F6%5E2%22%22-%22%22%28y-1%29%5E2%2F28%22%22=%22%221
    
%28x-4%29%5E2%2F36%22%22-%22%22%28y-1%29%5E2%2F28%22%22=%22%221

Edwin