x²+y²-2（m+3）x+2（1-4m²）y+16m^4+9=0
(x-m-3)²+(y+1-4m²）²=m²+6m+9+1-8m²+16m^4-16m^4-9
(x-m-3)²+(y+1-4m²）²=-7m²+6m+1
r²=-7m²+6m+1＞0
7m²-6m-1＜0
(7m+1)(m-1)＜0
-1/7＜m＜1