Problem 1 · Numerical methods
Select all that apply.
Select all statements that are true of Newton's method for finding a root of f(x) = 0.
- A.Near a simple root it converges quadratically.
- B.It converges from any starting point.
- C.It can fail or diverge when f′(xₙ) is close to zero.
- D.It requires a starting interval over which f changes sign.
- E.Each iteration requires evaluating the derivative f′(xₙ).
Show the answer and solution
Answer: A: Near a simple root it converges quadratically.; C: It can fail or diverge when f′(xₙ) is close to zero.; E: Each iteration requires evaluating the derivative f′(xₙ).
Newton's update xₙ₊₁ = xₙ − f(xₙ)/f′(xₙ) needs the derivative at every step, roughly doubles the number of correct digits per iteration near a simple root, and takes huge or undefined steps when f′ is near zero. It starts from a single guess, and a poor guess can make it diverge or converge to a different root.
Numerical methods · Reference Handbook: Mathematics
