设二元函数f(x，y)=√(4x-y2)/ln(1-x2-4y2),则函数(t)=lim(x,y)→(t,0)f(x，y)的定义

设二元函数f(x，y)=√(4x-y2)/ln(1-x2-4y2),则函数(t)=lim(x,y)→(t,0)f(x，y)的定义域为____.
【正确答案】：(0，1].