Question

Which equation represents a circle?

a. `(x – 2)^2/(2^2) + (y – 3)^2/(3^2) = 1`
b. `(x – 4)^2/(3^2) + (y + k)^2/(1^2) = 1`
c. `(x^2)/(2^2) + (y^2)/(2^2) = 1`
d. `(x^2)/(1^2) + (y^2)/(3^2) = 1`?

Answer 1

C. Multiple each side by 4 and you get the radius as 2 and the center at 0,0.

Answer 2

Option C

Explanation:

Equation of a circle is in the form of

`(x-h)^2+(y-k)^2= r^2` where (h,k) is the center and r is the radius of the circle.

For equation of a circle, the denominator should be same

first , second and fourth equation have different denominators. so they are not equation of circles.

2^2 is 4

Multiply the whole equation by 4

So the equation becomes

`x^2+y^2= 4` that represents the equation of a circle