f(2x-1)的定义域为[0,1)
0<=x<1
0<=2x<2
-1<=2x-1<1
所以f(x)定义域是[-1,1)
则f(1-3x)中-1<=1-3x<1
-2<=-3x<0
0所以定义域是(0,2/3]