Hello from MrBillDoesMath!
Answer:
x = 0, 7
Discussion:
f(g(x)) =
f ( x^2-7x) =
1/ ( x^2 - 7x)
The points NOT in the domain are those where the denominator, x^2 - 7x = 0.
x^2 - 7x = 0 => factor x from each term
x(x-7) = 0 => one or both terms must each 0
x = 0 or x =7
Thank you,
MrB