Question

What is the equation of a circle centered at (-3,1) with radius 7?

Answer 1

The standard form of a circle is $(x-h)^2+(y-k)^2=r^2$, where h and k are the coordinates of the center and r is the radius.  We will fill in accordingly with what we have. $(x-(-3))^2+(y-1)^2=7^2$.  Simplifying a bit we have $(x+3)^2+(y-1)^2=49$.  That's the equation for your circle.