根据题意得配方得：(x-t-3)^2+(y+1-4t^2)^2 =-(7t+1)(t-1)-(7t+1)(t-1)>0-1/7＜t＜1配方：[x-(t+3)]^2+[y+(1-4t^2)]^2=(t+3)^2+(1-4t^2)^2-16t^4-9[x-(t+3)]^2+[y+(1-4t^2)]^2=-7t^2+6t+1[x-(t+3)]^2+[y+(1-4t^2)]^2...