FP1 chapter 2

Hi so I'm learning linear interpolation and the examples suggest that the formual is QR/RP=QB/PA but if we take the first question for example it uses PA/QB and I don't understand why? The rest of the questions follow too and I'm quite confused about how to do this :confused:

Reply 1

TeeEm

Original post by Teddysmith123

post an example

Reply 2

Teddysmith123

Original post by TeeEm

post an example

Ok so 5X^3-8X^2+1=0 has a root between X=1 and X=2
Find this root using linear interpolation correct to one decimal place.

Reply 3

TeeEm

Original post by Teddysmith123

Ok so 5X^3-8X^2+1=0 has a root between X=1 and X=2
Find this root using linear interpolation correct to one decimal place.

call it f(x) and find f(1) and f(2) next

Reply 4

Teddysmith123

Original post by TeeEm

call it f(x) and find f(1) and f(2) next

Yh so thats easy f(1) = -2 and F(2) = 9

Reply 5

Teddysmith123

Original post by TeeEm

call it f(x) and find f(1) and f(2) next

It's the next step I find confusing

Reply 6

TeeEm

Original post by Teddysmith123

It's the next step I find confusing

(2-a)/(a-1) = 9/|-2|

can you see where each number comes from

solve to get a

Reply 7

Teddysmith123

Original post by TeeEm

(2-a)/(a-1) = 9/|-2|

can you see where each number comes from

solve to get a

Thats what I thought I had to do but on solution bank it does 2/9 which is why I was unsure

Reply 8

TeeEm

Original post by Teddysmith123

Thats what I thought I had to do but on solution bank it does 2/9 which is why I was unsure

probably a typo

Reply 9

Teddysmith123

Original post by TeeEm

probably a typo

But it does it for the question before it too and again on another question

https://644625398389466aee00633223056f55519d5fbc.googledrive.com/host/0B1ZiqBksUHNYQWY1UWtNa0NRNU0/CH2.pdf

Look at exercise 2B page 7, question 1, 2 and 5

For question 5 can someone explain why the denominator is always 1?

Reply 10

TeeEm

Original post by Teddysmith123

I have not got the faintest idea what "they" are saying

Either I have lost the plot

or

what you are showing me is mathematics from someone who escaped from a lunatic asylum.

Reply 11

Teddysmith123

Original post by TeeEm

I have not got the faintest idea what "they" are saying

Either I have lost the plot

or

what you are showing me is mathematics from someone who escaped from a lunatic asylum.

This has been driving me crazy all day since I thought I understood how to do these questions but then I saw this!

Reply 12

TeeEm

Original post by Teddysmith123

This has been driving me crazy all day since I thought I understood how to do these questions but then I saw this!

look at these 2 examples

numerical_solutions_of_equations.pdf

Reply 13

Teddysmith123

Original post by TeeEm

look at these 2 examples

numerical_solutions_of_equations.pdf

Thanks you! I just did both examples and got them right so I guess it was just a mix up with the edexcel book!

Reply 14

TeeEm

Original post by Teddysmith123

Thanks you! I just did both examples and got them right so I guess it was just a mix up with the edexcel book!

I guess.

Talk to your teacher tomorrow...

Reply 15

Notnek

Original post by Teddysmith123

Thanks you! I just did both examples and got them right so I guess it was just a mix up with the edexcel book!

I remember there being mistakes in the solutionbank of that textbook for some linear interpolation FP1 questions.

These are probably the mistakes.

Reply 16

Teddysmith123

Original post by notnek

I remember there being mistakes in the solutionbank of that textbook for some linear interpolation FP1 questions.

These are probably the mistakes.

Yh I think thats right which is annoying! I did do some exam questions on linear interpolation and I got those right so I'm just going to ignore the exercise and move on