笔记归档-牛顿迭代法
If the tangent line is approaching a function, we expect the tangent line to have a root approaching the function's root.
Using Newton's rule to calculate square root:
For
f(x)=x^2-a
f`(x)=2x
x_n+1=x_n-((x_n)^2-a)/2x_n=1/2(x_n+a/x_n)
tangent line: y=f(x_0)+f`(x)(x-x_0)
to find x_0, let y=0
0=f(x_0)+f`(x)(x_1-x_0)
-f(x_0)=f`(x_0)(x_1-x_0)
-f(x_0)/f`(x_0)=x_1-x_0
If f(x_1)!=, then take a tangent line here
y=f(x_1)+f`(x_1)(x-x_1)
Find the x-int(or find x_2)
0=f(x_1)+f`(x_1)(x_2-x_1)
x_2=x_1-f(x_1)/f`(x_1)
Herative Formula for Newton's Method:
x_(n+1)=x_n-f(x_n)/f`(x_n)