Question

What is the radius of the circle whose equation is x2 + y2 = 9?
3
9
81

Answer 1

Answer: The radius of the circle is (A) 3 units.

Step-by-step explanation: The given equation of the circle is

`x^2+y^2=9.~~~~~~~~~~~~~~~~~~~(i)`

We are to find the radius of the circle represented by the equation (i).

The standard form of a circle with center (g, h) and radius 'r' units is given by

`(x-g)^2+(y-h)^2=r^2.`

From equation (i), we have

`x^2+y^2=9\\\\\Rightarrow (x-0)^2+(y-0)^2=3^2.`

This represents a circle with centre at the origin (0, 0) and radius 3 units.

Therefore, the radius of the given circle is 3 units.

Thus, (A) is the correct option.

Answer 2

The center-radius form of the circle equationis in the format (x – h)2 + (y – k)2 = r2, with the center being at the point (h, k) and the radius being "r". Therefore the radius of the circle with the given equation would be √9 or 3, first option. Hope this answers the question.