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Newton’s Method

Newton's Method

An iterative process using derivatives that can often (but not always) be used to find zeros of a differentiable function. The basic idea is to start with an approximate guess for the zero, then use the formula below to turn that guess into a better approximation. This process is repeated until, after only a few steps, the approximation is extremely close to the actual value of the zero.

Note: In some circumstances, Newton's method backfires and gives successively worse and worse approximations.

Newton's Method formula x_{n+1} = x_n - f(x_n)/f'(x_n), with example approximating √2 using f(x)=x²-2, starting at x₁=1.5,...