Math  /  Geometry

QuestionFind the foci of the hyperbola defined by the equation (y+4)281(x+8)249=1\frac{(y+4)^{2}}{81}-\frac{(x+8)^{2}}{49}=1. If necessary round to the nearest tenth.
Answer Attempt 1 out of 2
Foci: \square , \square ) and ( \square , , )

Studdy Solution

STEP 1

What is this asking? We need to find the two focal points of a hyperbola centered at (8,4)(-8, -4) with a vertical main axis. Watch out! Don't mix up the formulas for ellipses and hyperbolas!
Also, remember the center isn't at (0,0)(0, 0)!

STEP 2

1. Identify key features of the hyperbola.
2. Calculate cc.
3. Find the foci.

STEP 3

Alright, let's **break down** this hyperbola equation!
We've got (y+4)281(x+8)249=1\frac{(y+4)^{2}}{81}-\frac{(x+8)^{2}}{49}=1.
This tells us a few things.
First, the **center** of the hyperbola is at (8,4)(-8, -4).

STEP 4

Next, since the yy term is positive, we know this hyperbola opens **vertically**.
The value under the yy term is 81=a281 = a^2, so a=9a = 9.
The value under the xx term is 49=b249 = b^2, so b=7b = 7.

STEP 5

For hyperbolas, the relationship between aa, bb, and cc (where cc is the distance from the center to each focus) is c2=a2+b2c^2 = a^2 + b^2.
It's like the Pythagorean theorem, but with a **plus** instead of a minus!

STEP 6

Let's **plug in** our values: c2=92+72=81+49=130c^2 = 9^2 + 7^2 = 81 + 49 = 130.
So, c=13011.4c = \sqrt{130} \approx \mathbf{11.4}.

STEP 7

Since our hyperbola opens vertically, the foci will be cc units **above and below** the center.
The x-coordinate of the foci will be the same as the center's x-coordinate, which is 8-8.

STEP 8

The y-coordinates of the foci will be the center's y-coordinate, 4-4, plus or minus cc.
So, the foci are at (8,4+130)(-8, -4 + \sqrt{130}) and (8,4130)(-8, -4 - \sqrt{130}).

STEP 9

Using our approximation for cc, the foci are approximately at (8,4+11.4)(-8, -4 + 11.4) and (8,411.4)(-8, -4 - 11.4), which simplifies to (8,7.4)(-8, 7.4) and (8,15.4)(-8, -15.4).

STEP 10

Foci: (8,7.4)(-8, 7.4) and (8,15.4)(-8, -15.4)

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