Question

x^2+y^2+4x-2y=-1 The equation of a circle in the xy plane is shown above. What will be the radius? a) 2 b)3 c)4 d)9

Answer 1

Answer:

2

Step-by-step explanation:

$x^{2} +y^{2} +4x -2y+1=0$

Comparing with $x^{2}+ y^{2}+2gx+2fy+c=0$

g= 2         f=-1    c=1

Radius =$\sqrt{g^{2}+f^{2} -c }$

             =$\sqrt{4+1-1}$

             = $\sqrt{4}$

Radius   = 2

Answer 2

Answer:

2

Step-by-step explanation:

x^{2} +y^{2} +4x -2y+1=0x

2

+y

2

+4x−2y+1=0

Comparing with x^{2}+ y^{2}+2gx+2fy+c=0x

2

+y

2

+2gx+2fy+c=0

g= 2 f=-1 c=1

Radius =\sqrt{g^{2}+f^{2} -c }

g

2

+f

2

−c

=\sqrt{4+1-1}

4+1−1

= \sqrt{4}

4

Radius = 2