Questions / Quant development, Numerics & testing
Recover the small root without cancellation
For x² − 10x + 1 = 0, compute the small root with 2/(B + √(B² − 4)), B = 10.
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Answer: 0.101 value
- √(100 − 4) = √96 ≈ 9.79796.
- B + √(B² − 4) ≈ 19.79796.
- 2/19.79796 ≈ 0.101021.
Interview shortcut. 2/(10 + √96) ≈ 0.1010.
Takeaway. Rewrite to avoid subtracting nearly equal numbers.
In the app this has a follow-up where one thing about the setup changes. Try the follow-up.