Let f(x) = \frac{1}{1+\frac{2}{1+\frac 3x}}. There are three real numbers x that are not in the domain of f(x). What is the sum of those three numbers?
f(x)=11+21+3x
From the bottom
x cannot = 0
1 + 1/x = [x + 1] / x
1 / ( [ x + 1] / x) = x / [x + 1]
x cannot be -1
1 + x / [x + 1] = [ 2x + 1 ] / [ x + 1]
1 / [ (2x + 1) / (x + 1) ] = (x + 1) / (2x + 1)
x cannot be -1/2
sum = 0 - 1 - 1/2 = -3/2
+972 
