Question

Find the center and radius of the circle with equation x^2 + y^2 -2x + 4y - 11 = 0

Answer 1

Answer:

An equation of the circle with center (h, k) and radius ris

(x - h)² + (y - k)² = r²

Consider, x² + y² + 4y = 0, it can be rewritten

as:

x² + y² + 4y +4= 0+4

implies (x + 0)² + (y + 2)² = 4

So, comparing (x+0)² + (y + 2)² = 4 with the

above equation of circle we get:

h = 0, k=-2 and r = 2 Therefore, center of the circle is (0, -2) and radius of the circle is r = 2.