#r=-8(cos x+sinx)#
#r^2=-8r(cosx+sinx)#-> multiply both sides by r
#r^2=-8rcosx-8rsinx#->distribute
#x^2+y^2=-8x-8y#->use formula #x=rcos theta, y=rsin theta#
#x^2+8x+y^2+8y=0#
#(x^2+8x+16)+(y^2+8y+16)=16+16#-> complete the square
#(x+4)^2+(y+4)^2=32#