I mean, you can. "Have an initial idea. Define a utility function. Apply gradient descent".
It's just that all three steps are really really hard.
TDDs insight is that gradient descent is relatively easy if the utility function is one-dimensional and monotonic. (Bonus point, it still works with the set of initial ideas being empty)
The "tricks in your toolbox" are ultimately all about simplifying the utility function from "exhaustive mapping of problem domain to solution demain proves valid" to a simpler one. In your example, you mapped the problem domain from "solve order two polynomial" to "complete square, take square root, solve order one polynomial".
You _could_ apply these tricks mechanically (hey, that's what symbolic algebraic systems do in your example), but it would require an initial formal specification of the problem - that's ultimately what Norvig does for his Sudoku approach - and, for a general approach, a way to reason over formal specifications.
It always boils down to "how well do you understand the problem, and how well can you describe it formally". TDD works best for "not at all, not at all".