Let `f` be a differentiable function defined for `x > 2` such that
`int_3^(ab + 2) f (x)\ dx = int_3^(a + 2) f(x)\ dx + int_3^(b + 2) f(x)\ dx` where `a > 1 and b > 1.`
The rule for `f (x)` is
- `sqrt (x - 2)`
- `log_e (x - 2)`
- `sqrt (2x - 4)`
- `log_e (2x - 2)`
- `1/(x - 2)`