# Math Help - Newtons Method

1. ## Newtons Method

I need a little help solving this problem by using newtons method:

Find x where y=6e^-x+6e^-2x+106e^-3x

2. Do we have to rearrange it to make x the subject or does y equal something?

3. I'm guessing it's $y=f(x)$, so we use Newton-Raphson's method to find the root.

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

Try using $x_0 = 4$

4. Originally Posted by Spec
I'm guessing it's $y=f(x)$, so we use Newton-Raphson's method to find the root.

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

Try using $x_0 = 4$
Actually its

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

5. Right, good catch.

6. so apply that formula and im good?

7. You might have to do a few iterations to get close enough to the solution.

8. Originally Posted by Luck of the Irish
so apply that formula and im good?
Yes, assuming that the problem is to solve the equation 6e^-x+6e^-2x+106e^-3x= 0. You never have said that.