With IPFS you access content by hash. So if you have a plain IPFS link to "Lagrange multiplier", it will always point to exactly the same version you are looking at right now. No way to change or update that.
If you want to update content, you have to point the user to a new hash. IPFS has the IPNS mechanism for that, this adds a layer of indirection, so instead of pointing to the IPFS hash directly, you point to the IPNS name which in turn points to the current hash. What an IPNS name is pointing to can be updated by the owner of that IPNS name.
Another option is to do in via plain old DNS and have the DNS record point to the current hash of the website.
