x^2*(x-6)^2+14(x-3)^2=81 x-3=t ((t+3)*(t-3))^2+14t^2-81=0 (t^2-9)^2+14t^2-81=0 t^4-4t^2=0 t=0 x=3 t=2 x=5 t=-2 x=1