Question

What is the diameter of the following circle: (x + 4)2 + (y – 9)2 = 18

Answer 1

diameter =2r

Answer 2

Circle \((x - h)^2 + (y - k)^2 = r^2\) has radius r and diameter 2r.

Answer 3

so times 18 by 2?

Answer 4

No.
18 is r^2.
First find r. Then multiply it by 2.

Answer 5

im confused

Answer 6

is is another word for equal
r^2=18 <--can you solve this for r so that you have the radius

Answer 7

so r is 9 ?

Answer 8

hmm 9^2=9(9) isn't 18

Answer 9

I'll give you an example:
In the circle \((x - 4)^2 + (y - 3)^2 = 9\),
the center is (4, 3), and the radius is 3, since 3^2 = 9.
You take the square root of 9 and get 3. That is the radius.

Answer 10

In your case. r^2 = 18
Take the square root of 18 to find the radius.
Then multiply the radius by 2 to find the diameter.

Answer 11

so it'll be 8.48?

Answer 12

You probably need an exact answer.
This is how you do it.
\(r = \sqrt{18}\)
\(d = 2\sqrt{18} = 2 \sqrt{9 \cdot 2} = 2 \sqrt{9}\sqrt{2} = 2 \cdot 3\sqrt{2} = 6\sqrt2\)