Question

The equation for the circle below is the x2 + y2=81. what is the length of the circles radius

Answer 1

Answer:

9

Step-by-step explanation:

Compare your x2 + y2=81 to the following:

                       x^2 + y^2 = 81

The " ^ " symbol indicates exponentiation.

Now compare  x^2 + y^2 = 81 to

                         x^2 + y^2 = r^2.  

This is the standard equation of a circle of radius r centered at the origin, (0,0).  You can see for yourself that 81 must equal r^2.

Taking the square root of 81, we get plus or minus 9.

But the radius must be positive, so we reject the -9 and take +9.

The radius is 9.

Answer 2

Answer: 9

Step-by-step explanation: