Need help with newtons method Q___Q!! (1 Viewer)

[Oreo4rt]

Hey so i'm getting a little frustrated because i keep getting the wrong approximations for some newtons method questions. Help is greatly appreciated!!

Use one iteration of Newton's method to find an approx. to the root of equation xlnx-2x =0 near x=7.

i differentiated the equation and got lnx -1
then subbed everything into the equation x - f(x)/f'(x) : 7 - f(7)/f'(7) and got the answer 7.4 ( 1dp) but the answer says its 6.6

What did i do wrong?

 

[umm what]

Srsly? -.-

 

[Oreo4rt]

yes i know its meant to be easy but this questions just annoying me because i keep getting the wrong answer wth

 

[Trebla]

The answer is wrong. You are correct.

 

[Parvee]

The answer is wrong. You are correct.

^
I just did the question and got 7.4

 

[Oreo4rt]

Thanks Trebla and parvee! Argh i hate it when that happens

 

[Oreo4rt]

I've got a few more questions with the same problem... my answers dont match which the booklets answers... Would anyone please mind double checking?
i ) cosx -2x =0 starting with x=1/2 to 1 dp
ii) lnx + sinx =0 starting with x= 1/2 to 1 dp

 

[Trebla]

Hot tip: Graph the function on a graphing program and check whether your new approximation actually gets closer to the real root

 

[Shadowdude]

Hot tip: Graph the function on a graphing program and check whether your new approximation actually gets closer to the real root

i.e. for most of us: wolframalpha

 

[Sy123]

Geogebra is a good alternative and is easily adjustable compared to wolframalpha, but its a little less powerful