SOLUTION: I cannot seem to find the correct standard equation, foci, and asymptotes of the following hyperbola: {{{ x^2-4y^2-6x-16y-11=0 }}} I need to write it in this kind of form: {

Algebra ->  Quadratic-relations-and-conic-sections -> SOLUTION: I cannot seem to find the correct standard equation, foci, and asymptotes of the following hyperbola: {{{ x^2-4y^2-6x-16y-11=0 }}} I need to write it in this kind of form: {      Log On


   



Question 196705: I cannot seem to find the correct standard equation, foci, and asymptotes of the following hyperbola:
+x%5E2-4y%5E2-6x-16y-11=0+

I need to write it in this kind of form:
+%28%28%28x-h%29%5E2%29%2Fa%5E2%29-%28%28%28y-k%29%5E2%29%2Fb%5E2%29=0+

I have been solving these kinds of problems wrong lately, and I am quite worried since it will be a subject on an upcoming test. Any help would be appreciated, and many thanks in advance.

Answer by Edwin McCravy(20056) About Me  (Show Source):
You can put this solution on YOUR website!
I cannot seem to find the correct standard equation, foci, and asymptotes of the following hyperbola:
+x%5E2-4y%5E2-6x-16y-11=0+

Rearrange so that the two terms in x are next to
each other and the two terms in y are next to
each other, and 11 to both sides:
sides:

x%5E2-6x-4y%5E2-16y=11

The coefficient of x%5E2 is already 1, so
we don't factor anything out of it, just enclose the
first two terms in parentheses:

%28x%5E2-6x%29-4y%5E2-16y=11

Now factor only -4 (not y) out of the last two terms
on the left.

%28x%5E2-6x%29-4%28y%5E2%2B4y%29=11

Complete the square in each parentheses.  

In the first parentheses multiply the -6 coefficient of
x by 1%2F2, getting -3.  Then we square -3,
getting %28-3%29%5E2=9.  So we add 9 to both sides:

%28x%5E2-6x%2B9%29-4%28y%5E2%2B4y%29=11%2B9

%28x%5E2-6x%2B9%29-4%28y%5E2%2B4y%29=20

Now we factor the first parentheses as %28x-3%29%28x-3%29
or %28x-3%29%5E2

%28x-3%29%5E2-4%28y%5E2%2B4y%29=20

In the second parentheses multiply the 4 coefficient of
y by 1%2F2, getting 2.  Then we square 2,
getting %282%29%5E2=4.  So we add 4 inside the second
parentheses.

But since there is a -4 factor in front of the second
parentheses, when we add 4 inside the second parentheses
we are really adding -4 times 4 or -16 to the
left side, so we must add -16 to the right side too.

%28x-3%29%5E2-4%28y%5E2%2B4y%2B4%29=20-16

%28x-3%29%5E2-4%28y%5E2%2B4y%2B4%29=4

Now we factor the second parentheses as %28y%2B2%29%28y%2B2%29
or %28y%2B2%29%5E2

%28x-3%29%5E2-4%28y%2B2%29%5E2=4

Next we get a 1 on the right side by dividing
through by 4

%28%28x-3%29%5E2%29%2F4-4%28y%2B2%29%5E2%2F4=4%2F4

%28%28x-3%29%5E2%29%2F4-4%28y%2B2%29%5E2%2F4=1

Now to get rid of the 4 on top on the second term, we
divide top and bottom by 4

%28%28x-3%29%5E2%29%2F4-%28%284%28y%2B2%29%5E2%29%2F4%29%2F%284%2F4%29=1

%28%28x-3%29%5E2%29%2F4-%28%28cross%284%29%28y%2B2%29%5E2%29%2Fcross%284%29%29%2F1=1

%28%28x-3%29%5E2%29%2F4-%28%28y%2B2%29%5E2%29%2F1=1

Can you go from here? 

Compare to

%28%28x-h%29%5E2%29%2Fa%5E2-%28%28y-k%29%5E2%29%2Fb%5E2=1

So h=3, k=-2, a=2, b=1

So center = (h,k) = (3,-2)

The two vertices are a=2 units left and right of the
center, so they are (1,-2) and (5,-2)

The two foci are c units left and right of the center.

First we calculate c using

c%5E2=a%5E2%2Bb%5E2
c%5E2=2%5E2%2B1%5E2
c%5E2=4%2B1
c%5E2=5
c=sqrt%285%29

So the two foci are c=sqrt%285%29 units left and right of the
center, so they are (3-sqrt%285%29,-2) and (3%2Bsqrt%285%29,-2)

The asymptotes have slopes which are ±b%2Fa or
±1%2F2

And the go through the center (3,-2), so we use the
point slope formula:

For the asymptote that has slope 1%2F2:

y%2B2=%281%2F2%29%28x-3%29

Multiply both sides by 2

2y%2B4=x-3

-x%2B2y=-7

x-2y=7

---------------

For the asymptote that has slope -1%2F2:

y%2B2=%28-1%2F2%29%28x-3%29

Multiply both sides by -2

-2y-4=x-3

-x-2y=1

x%2B2y=-1
 
Edwin