Hi! I am new here and need some help. I am doing a maths course at home through Open Uni and I have got stuck.

The equation

x^2 + 10x + y^2 - 6y + 9 = 0

represents a circle. Find the centre and it's radius.

I have had a look around online at other examples and it says to put it in a certain format with h,k & r. But I just can't follow it to make the equation given here fit in. Can anyone give me some guidance and help working it out please?