Draw a graph

This is the graph x^2+y^2=4, (square root 2= 4), draw the line in 2 ,a circle!http://www.quickmath.com/pages/modules/graphs/equations/

Plot x^2 + y^2 = 1, x^2 + y^2 = 4, x^2 + y^2 = 9, x^2 + y^2 =16 ,x^2 + y^2 = 25 and x^2 + y^2 =36 from x = -6 to x = 6, y = -6 to y = 6 (like square root the answers 1, 4,9,16,25,36)   http://www.quickmath.com/pages/modules/graphs/equations/

Page 1 Graph

Page 2 Graph