Question

What is the equation of this circle?
The circle is featured in the image below.

Answer 1

Step 1:

The circle is offset to the left of the origin by 1, so we know that the equation must include (x+1). Addition to the x value moves a circle to the left, while subtraction moves it to the right.

Step 2:

The circle is offset upwards by 2, so we know that the equation must include (y-2). Addition to the y value moves a circle down, while subtraction moves it up.

Step 3:

We can see that the radius of the circle is 3, because the distance from the middle to any endpoint is 3. 3 squared is 9, so the right side of the equation must have a 9.

Answer:

The answer is C.

`\left(x+1\right)^(2)+\left(y-2\right)^(2)=9\\`