nd Find the center aradius of the circle whose equation is given.?

Question

x2 + y2 + 4x - 5 = 0

Answer 1

Complete the square on x^2 + 4x+___ (half of 4, is 2, square that to get 4). So add 4 to both sides to get
x^2+4x+4+y^2=5+4
=>(x+2)^2+y^2=9
The center is at (-2,0), and the radius is 3.

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

Answer 2

Write it as x^2 +4x +y^2 = 5.
Now complete the square in x:
x^2 + 4x + 4 + y^2 = 9
i.e.,
(x+2)^2 + y^2 = 9.
So the center is at (-2,0) and the radius is 3.