Hello Guest,
x2+y2=2−x−6y+6−18x+2y
Move the variables to the left side and change their signs
x2+y2−2x+6y+18x−2y=6
x2+y2+16x+6y−2y=6
x2+y2+16x+4y=6
Use the commutative property to reorder the terms
x2+16x+y2+4y=6
To complete the square, the same value needs to be added to both sides
x2+16x+?+y2+4y=6+?
To complete the square x2+16x+64=(x+8)2 add 64 to the expression
x2+16x+64+y2+4y=6+?
Since 64 was added to the left side, also add 64 to the right side
x2+16x+64+y2+4y=6+64
Use the first binomial a2+2ab+b2=(a+b)2 to factor the expression
(x+8)2+y2+4y=6+64
(x+8)2+y2+4y=70
To complete the square, the same value needs to be added to both sides
(x+8)2+y2+4y+?=70+?
To complete the square y2+4y+4=(y+2)2 add 4 to the expression
(x+8)+y2+4y+4=70+?
Since 4 was added to the left side, also add 4 to the right side
(x+8)+y2+4y+4=70+4
Use the first binomial a2+2ab+b2=(a+b)2 to factor the expression
(x+8)2+(y+2)2=70+4
(x+8)2+(y+2)2=74
The equation can be written in the form (x−p)2+(y−q)2=r2 , so it represents a circle with the radius r=√74 and the center (−8,−2)
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