Consider the TRS R consisting of the rewrite rules

1: f(f(X)) -> f(a(b(f(X))))
2: f(a(g(X))) -> b(X)
3: b(X) -> a(X)

There are 3 dependency pairs:

4: F(f(X)) -> F(a(b(f(X))))
5: F(f(X)) -> B(f(X))
6: F(a(g(X))) -> B(X)

The approximated dependency graph contains no SCCs
and hence the TRS is trivially terminating.