Using the following equation, find the center and radius:

x2 + 2x + y2 + 4y = 20

centre = (- 1, - 2 ) , radius = 5

Step-by-step explanation:

The equation of a circle in standard form is

(x - h)² + (y - k)² = r²

where (h, k) are the coordinates of the centre and r is the radius

Given

x² + 2x + y² + 4y = 20

To obtain equation in standard form use method of completing the square

add ( half the coefficient of the x/y terms )² to both sides

x² + 2(1)x + 1 + y² + 2(2)y + 4 = 20 + 1 + 4

(x + 1)² + (y + 2)² = 25 = 5² ← in standard form

with centre = (- 1, - 2 ) and r = 5

step-by-step explanation: