>>166
x = 0.7;
a2 =.;
y = a2 + (7*(-1 + x))/(1 + 2*x);
rule1 = Solve[y == 0, a2][[1]];
ParametricPlot[{{r1 = 1 + a2*LegendreP[2, Cos[q]] /. rule1; r1*Cos[q],
r1*Sin[q]}}, {q, 0, 2*Pi}, AspectRatio -> Automatic];