A certain circle can be represented by the following equation. x 2 + y 2 + 1 8 x + 1 4 y + 1 0 5 = 0 x 2 +y 2 +18x+14y+105=0

Question

what is the radius and the center of the circle

 

Answer 1

Complete the square (in both x and y) to get into form (x-h)^2 + (y-k)^2 = r^2

from which you learn that center is at (h,k) and radius is r.

 

This is a standard activity in Algebra II and your textbook will abound with examples.