mattamz just subbed numbers into the equation of a circle ie.
(x-h)^2 + (y-k)^2 = r^2
where, (h,k) is the centre of the circle and (x,y) are points that lie on the circle and r is the radius.
since your circle has centre (-3,4) subb that in for your centre (h,k) first and you get.
(x-(-3))^2...