方程x^2+y^2-2(t+3)x+2(1-4t^2)y+16t^4+9=0表示圆方程,t范围

[x-(t+3)]²+[y+(1-4t²)]²=-16t^4-9+(t+3)²+(1-4t²)²
是圆则r²=-16t^4-9+(t+3)²+(1-4t²)²>0
t²+6t+1-8t²>0
7t²-6t-1