Question

13. Find the center and radius for each of the following circles: (c) (x + 1)2 + (y - 1) = 4

Answer 1

The general equation of the circle is :

$(x-h)^2+(y-k)^2=r^2$

Where r is the radius of the circle

And ( h , k ) is the center of the circle

Given the equation :

$(x+1)^2+(y-1)^2=4$

making the given equation like the general form :

$(x-(-1))^2+(y-1)^2=2^2$

So, by comparing the equations :

$\begin{gathered} h=-1 \\ k=1 \\ r=2 \end{gathered}$

So, the center of the circle = ( h , k ) = ( -1 , 1 )

And the radius of the circle = r = 2