Find all the real zeros of the function.

1. f(x) = x^3 - 2x^2 - 23x + 60

2. g(x) - x^3 - 28x - 48

3. h(x) = x^3 + 10x^2 + 31x + 30

4. f(x) = x^3 - 14x^2 + 55x - 42

5. p(x) = 2x^3 - x^2 - 27x + 36

6. g(x) = 3x^3 - 25x^2 + 58x - 40