There are three real numbers x that are not in the domain of \[f(x) = \cfrac{1}{1+\cfrac{2}{1+\cfrac 3x}}.\] What is the sum of those three numbers?
X = 0
1+1/x=0
x+1=0
x=-1
1+1/(1+1/x) = 0
1 + 1/x + 1 = 0
2+ 1/x = 0
2x +1 = 0
2x = -1
x = -1/2
0+(-1)+(-1/2)=-3/2
0 and -3 and -1
