Im having trouble answering questions like this, any help would be much appreciated.
Find the centre and radius of the circle with equation
$\displaystyle x^2+y^2-6x-2y-6=0$
If you are not familiar with the technique of completing the square, then you should review it.
In this example, we have
$\displaystyle x^2+y^2-6x-2y-6=0$
$\displaystyle \Rightarrow(x^2-6x+9)+(y^2-2y+1)=16$
$\displaystyle \Rightarrow(x-3)^2+(y-1)^2=4^2\text.$
Now can you see the center and radius?