# Math Help - Newton's Method

1. ## Newton's Method

Apply newton's method to the equation $x^2-a=0$ to derive the following square-root algorithm: $Xn+1= \frac12(Xn+a/Xn)$

$f(x)=x^2-a$
$f'(x)=2x$

What's next?...

2. Come on guys... I really need help

3. Originally Posted by Fosite
Apply newton's method to the equation $x^2-a=0$ to derive the following square-root algorithm: $Xn+1= \frac12(Xn+a/Xn)$

$f(x)=x^2-a$
$f'(x)=2x$

What's next?...

Just plug into the formula for Newtons method

$x_{n+1}=x_n-\frac{f(x_n)}{f'(x_n)}$

and simplify and whola you are done

4. Originally Posted by TheEmptySet
Just plug into the formula for Newtons method

$x_{n+1}=x_n-\frac{f(x_n)}{f'(x_n)}$

and simplify and whola you are done
my question is which X1 should I choose? and is the final formula always contains $a$?