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can you please solve this equation with steps

e^(1/x)-x=0

 Jan 20, 2015

Best Answer 

 #3
avatar+118703 
+10

This is yet another formula that I have not memorised.  

I work it out every time.

 

 

(This is not presenting properly as fractions because LaTex is playing up!)

 

Consider the red tangent. $Thegradientofthislineisf(x0)$BUT The tangent is also =rise/run=(f(x0)0)/(x0x1)=f(x0)/(x0x1)f(x0)=f(x0)/(x0x1)f(x0)(x0x1)=f(x0)(x0x1)=f(x0)/f(x)x1=[f(x0)/f(x0)]x0x1=x0[f(x0)/f(x)]

 Jan 21, 2015
 #1
avatar+26396 
+10

e^(1/x)-x=0

Root-Finding Algorithm with Newton's method: \small{\text{ $ \boxed{ x_{i+1} = x_i - \dfrac{f(x_i)}{f'(x_i)} } \quad f{(x)} = e^{\frac{1}{x}}-x $ and $ f'(x) = -\frac{ e^{\frac{1}{x}}}{x^2}-1 $ we have $ x_{i+1} = x_i + \dfrac{ e^{\dfrac{1}{x_i}}-x_i } {\frac{ e^{ \left(\dfrac{1}{x_i} \right) } } {x_i^2}+1}  $ }

We start with:  

 x0=1  x1=1+e1e+1=1.46211715726  x2=1.46211715726+0.519552440511.92697260563=1.73173824009  x3=1.73173824009+0.049759570611.59404698875=1.76295411450  x4=1.76295411450+0.000421152331.56736524331=1.76322281532  x5=1.76322281532+0.000000029821.56714330612=1.76322283435  x6=1.76322283435+0.0000000000000001495443031.56714329041=1.76322283435 

x1.76322283435

 Jan 20, 2015
 #2
avatar+130466 
+8

Thanks, heureka.....

Notice how fast this coverges by using Newton's Method......the 4th and 5th terms agree to seven decimal places ....!!!!

 

 Jan 20, 2015
 #3
avatar+118703 
+10
Best Answer

This is yet another formula that I have not memorised.  

I work it out every time.

 

 

(This is not presenting properly as fractions because LaTex is playing up!)

 

Consider the red tangent. $Thegradientofthislineisf(x0)$BUT The tangent is also =rise/run=(f(x0)0)/(x0x1)=f(x0)/(x0x1)f(x0)=f(x0)/(x0x1)f(x0)(x0x1)=f(x0)(x0x1)=f(x0)/f(x)x1=[f(x0)/f(x0)]x0x1=x0[f(x0)/f(x)]

Melody Jan 21, 2015
 #4
avatar+130466 
+5

I'm afraid I have to run for the references whenever I have to use this too, Melody.....

It IS a pretty neat how it wotks, though.....and the concept is simple.....!!!

 

 Jan 21, 2015
 #5
avatar+118703 
+5

I do not run to references Chris.

I just work it out myself.  It is easy after you  have done it a few times.

 Jan 21, 2015

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