Answer:
[tex]x^2 + y^2 = 16[/tex]
Step-by-step explanation:
The center of a circle can be used to write the equation [tex](x-h)^2 + (y-k)^2 = r^2[/tex]. Notice h and k are the opposite value as in the equation.
Since the center is (0,0), substitute h=0 and k=0. Then substitute r = 4.
[tex](x-0)^2+(y-0)^2 = 4^2\\x^2 + y^2 = 16[/tex]
