Question

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Answer 1

x^2 + 2x + y^2 + 4y = 20

Answer 2

(x^2+2x)+(y^2+4y)=20

Completing the square
(X^2+2.1.x+1)-1+(y^2+2.2.y+4)-4=20
(X+1)^2+(y+2)^2=25

General equation of a circle
(X-a)^2+(y-b)^2=r^2

Answer 3

Where (a,b) is the center of circle and r is the radius