Question

A circle is shown on the coordinate plane below. What is the equation of this circle? (x – 1)2 + y2 = 2 (x + 1)2 + y2 = 4 (x + 1)2 + y2 = 2 (x – 1)2 + y2 = 4

Answer 1

WHERE IS CIRCLE?

Answer 2

here is the circle

Answer 3

ITS A

Answer 4

thank you (:

Answer 5

SO you are my fan

Answer 6

yes lol

Answer 7

lol????????????????

Answer 8

There are two ways to answer this question. If you don't know the equation of the circle, you could take a point on the circle (say x=-1, y=0), and try these in each of the possible answers. The correct equation will be true.

or, you might remember that the equation of a circle centered at (0,0) is
\[ x^2+y^2= r^2 \]
where r is the radius. Find the diameter (side to side, or bottom to top) and divide by 2
Here the diameter is 4, so the radius is 4/2= 2. and r^2= 2*2=4
so look for an equation with 4 on the right side. Then use the first trick to pick the correct answer.

or you might know the equation of the a circle centered at (x0,y0) is
\[ (x-x_0)^2 + (y-y__0)^2 =r^2 \]

to find the center, find the average of the x values on each side (-1+3)/2= 2/2= 1 for x
and y= (-2+2)/2=0
so x0= 1 and y0=0
use these in the equation to get the answer.

Answer 9

btw, the answer is not A