ContourPlot[x^2+y^2 == 26,{x,-8,8},{y,-8,8}]

Manipulate[ContourPlot[(((c*(x+d)))^2)+(((a*(y+b)))^2)==16,{x,-8,8},{y,-6,14},
                                                PlotPoints ->200],                             
                    {a,0.2,2,0.2}, {b,-4,4,0.5}, {c,0.2,3,0.2}, {d,-5,5,0.5}]