Find all positive integer solutions (n+21)/10 = ⌊√n⌋

Modified 2020 AMC 10B Problem 24 Did not see a solution at AoPS that was like this one(The approach of Isabel Chen was similar) where a simplifying Floor Function Lemma ⌊√n⌋=k⇔ k^2≤ n less than (k+1)^2 made counting and finding the positive integer solutions a relatively straightforward task. The ubiquitous complete the square process was used. This particular math problem is a decent example of relating the learning principle to assessment creation. Not sure what is meant by Low Quality mathematics Problems. Jeffrey Chen and Kevin Zhao wrote about this. Is it synonymous with problems that are too easy or problems they just don’t like. It is difficult to define quality in this sense just like what was referenced in Zen and the art of motorcycle maintenance by pirsig.

[@saffron1449]

You made it look so easy.
I am pretty sure i would have wasted at least half to one hour on this.

[@MyOneFiftiethOfADollar]

Thank you. I modeled it after a similar AMC problem or I would have spent a lot of time on it too! The lemma at beginning of problem is a big time saver.