# Problem Sheet J

This sheet is based on Lectures 19 and 20.

- Problem 1 show that strong deformation retractions really are stronger than normal deformation retractions.
- Problem 2 is just easy.
- Problems 3 and 4 introduce the Euler characteristic.
- Problem 5 asks you to come up
^{[1]}with an explicit isomorphism $ H_n(X) \cong H_n(X, \mathcal{F})$. - Problem 6 gives a categorical interpretation of cell-like filtrations.

As usual, feel free to ask questions if you are stuck! ðŸ˜€

Actually I thought this was a bit hard, so I pretty much just told you the answer. But you still need to verify what I claim works. â†©ï¸Ž

Comments and questions?