Question

2 circle questions...medals!

Answer 1

Do you know the form of the equation for a circle with radius r and center (h,k)?

Answer 2

\[\Large \left( x-h \right)^2+\left( y-k \right)^2=r^2\]

Answer 3

Just use the center and radius given in your problems. Remember that the origin has coordinates (0,0)

Answer 4

help please

Answer 5

can you so me how to do it step by step?

Answer 6

Here is the equation for a circle that has a radius of r, and a center at the point (h,k):

\[\Large \left( x-h \right)^2+\left( y-k \right)^2=r^2\]


So, for example, if I want the equation for a circle with radius of 5 and center (2,4), then I plug in r=5, h=2, and k=4:

\[\Large \left( x-2 \right)^2+\left( y-4 \right)^2=5^2\]

or,
\[\Large \left( x-2 \right)^2+\left( y-4 \right)^2=25\]

Make sense?

Answer 7

Just be careful with signs.... if I want a circle with r=1 and center (-2,4) then I get:

\[\Large \left( x+2 \right)^2+\left( y-4 \right)^2=1^2\]

Notice that the first piece, the one for (x-h) became a sum. Why? Because:

x-(-2)=x+2

Answer 8

ok

Answer 9

how do I find the answer?

Answer 10

I just showed you. Take the radius r and put it in for r. Take the center (h,k) and plug those values in for h and k. Simplify if necessary. That will give you the equation.

If you do it correctly, it will match one of your answer choices.

Answer 11

can you help me do the 1st problem?

Answer 12

Center is the origin, so (h,k)=(0,0). Radius is 11, so r=11.

Now you try it, and tell me what you get. I'll tell you if you are right or wrong.

Answer 13

(x-0)^2(y-0)=22?

Answer 14

B?

Answer 15

sorry, I was in another window....

Well, it is B, but I don't know where you got (x-0)^2(y-0)=22?

It would be \((x-0)^2(y-0)=11^2\)

which simplifies to \(x^2+y^2=121\)