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GCSE Iteration question

x^3-3x-1=0
The equation above has a solution in the interval 1<x<2 . Use the formula Xn+1= 3^(Cube root of 1+3xn.) given X0= 2 , compare values to 2.d.p to find this solution to 2.d.p

Reply 1

absolutelysprout

moving to maths forum- i'd recommend posting any working out you've done so help can be given quicker :smile:

Reply 2

username1732133

Original post by Querene

x^3-3x-1=0
The equation above has a solution in the interval 1<x<2 . Use the formula Xn+1= 3^(Cube root of 1+3xn.) given X0= 2 , compare values to 2.d.p to find this solution to 2.d.p

Did you mean

x_{n+1}=\sqrt[3]{3x_n+1}

Reply 3

Querene

Original post by entertainmyfaith

moving to maths forum- i'd recommend posting any working out you've done so help can be given quicker :smile:

Is it possible to post pictures because It’s really difficult and confusing to type these equations

Reply 4

username1732133

Original post by Querene

Is it possible to post pictures because It’s really difficult and confusing to type these equations

Yes, click on the paperclip symbol to add an attachment.

Reply 5

absolutelysprout

Original post by Querene

Is it possible to post pictures because It’s really difficult and confusing to type these equations

that's what most people do in the maths forum :yep:

Reply 6

Querene

Original post by BuryMathsTutor

Yes, click on the paperclip symbol to add an

Original post by entertainmyfaith

that's what most people do in the maths forum :yep:

Awh man I can’t find the paper clip :colondollar:

Reply 7

username1732133

Original post by Querene

Awh man I can’t find the paper clip :colondollar:

...

Untitled.png11.6KB

Reply 8

username4190740

this button qeqwtwrqty for phones?
Screenshot_2018-08-02-18-34-51-compressed.png.jpeg

(edited 5 years ago)

Reply 9

absolutelysprout

Original post by Querene

Awh man I can’t find the paper clip :colondollar:

is the toolbar not appearing for you where you can create a new post? (it's a bug atm) the paperclip symbol is there. if it's still not working upload the image to imgur, copy the link from there (by hovering your cursor over the image a little link on the photo should appear) and paste it here like this:

Reply 10

username1732133

Original post by TSRelif

this button qeqwtwrqty for phones?
Screenshot_2018-08-02-18-34-51-compressed.png.jpeg

We don't like the app in this forum because it doesn't handle our expressions, equations, identities or formulae.

Reply 11

gorilla558

Original post by Querene

x^3-3x-1=0
The equation above has a solution in the interval 1<x<2 . Use the formula Xn+1= 3^(Cube root of 1+3xn.) given X0= 2 , compare values to 2.d.p to find this solution to 2.d.p

sub x0's value into "x " in the equation value to get x1's value (ignore the little n near the x). Then sub x1 into x to get x2. sub x2's value into x to get x3's value. Do this about 5 times and you'd realise that there's less difference between values. The last few results will be very similar, sensibly round these to 2 decimal places.