When you're trying to choose between integration by parts and substitution, here are some easy tips to remember:

• Use Integration by Parts when:

  • You see two functions multiplied together, like $u \cdot dv$.
  • One of the functions is easy to take the derivative of.

• Use Substitution when:

  • You notice a clear inner function, like $g(x)$, that simplifies your work.

In simple terms, if you see a product of two functions, use integration by parts. But if there's a function inside another function, go with substitution!