Question

4. Find the center and radius of the circle with equation x2 + y2-2x + 4y -
11 = 0

Answer 1

(1 , -2) and r = 4

Explanation:

x² + y² - 2x + 4y - 11 = 0

x² - 2x + 1 - 1 + y² + 4y + 4 - 4 - 11 = 0

(x - 1)² - 1 + (y + 2)² - 4 - 11 = 0

(x - 1)² + (y + 2)² = 16

We know equation of circle is of the form

(x - h)² + (y - k)² = r²

So, center is (1 , -2) and radius is 4