[kenny629]

if i have f''(x) and take f'(x) i get f'(x)+c if i then take f(x) do i get f(x)+cx+c?
This is to find f(x) given 2 co-ordinates.
cheers!

[notnek]

Yes that's right although you should choose a different letter other than c for one of your constants.

Writing both constants as c assumes that they are equal.

[kenny629]

Of course! Didn't think of that, thanks!

[kenny629]

Am I able to find the function f(x) given a set of coordinates with 2 variables? Won't I be able to solve only for one??

[notnek]

(Original post by kenny629)
Am I able to find the function f(x) given a set of coordinates with 2 variables? Won't I be able to solve only for one??

Can you give an example just so it's clear what you mean?

[kenny629]

Sure, find f(x) I was given secon derivative, now I have taken the integral twice to give f(x), for example x^6+c(x)+n. given that it passes through (2,8) and (5,28). So I must find f(x)

[kenny629]

Y=f(x) sorry!!!

[notnek]

(Original post by kenny629)
Sure, find f(x) I was given secon derivative, now I have taken the integral twice to give f(x), for example x^6+c(x)+n. given that it passes through (2,8) and (5,28). So I must find f(x)

Since you've got two sets of coordinates, you should be able to find both constants.

Have you tried it? Post your working if you're stuck.

[ECONMATHSMATHSMATH]

Differentiation s the reverse of chain rule and vice versa!

[Maths_Lover]

(Original post by ECONMATHSMATHSMATH)
Differentiation s the reverse of chain rule and vice versa!

Huh?

The chain rule is a method of differentiation...

[kenny629]

For y=f(x) for the coordinate (2,8) I'd have 8=2^6+c(2)+n
Giving me 8=64+2c+n. Then y=56+(2c-8)+(n-8). Am I missing something really obvious here??? Don't want answers as such, just hints and tips. Thanks guys!

[Cephalus]

(Original post by ECONMATHSMATHSMATH)
Differentiation s the reverse of chain rule and vice versa!

lolololololololololololol since when? The chain rule is a rule for differentiating functions which is the product of two or more functions.

Do you mean differentiation is the reverse of integration?

[notnek]

(Original post by kenny629)
For y=f(x) for the coordinate (2,8) I'd have 8=2^6+c(2)+n
Giving me 8=64+2c+n. Then y=56+(2c-8)+(n-8). Am I missing something really obvious here???

I'm not sure where your y equation has come from. The equation in bold is correct and then you can use the second set of coordinates to construct a second equation. Then solve using simultaneous equations methods to find c and n.

Don't want answers as such, just hints and tips. Thanks guys!

You've come to the right place. You won't get solutions here, even if you ask for one

[kenny629]

Maybe I understood the question wrong, it says that y=f(x) passes through saud coordinates, find f(x), I'm guessing I should use this coordinates in f(x) then use simultaneous equations? And yes I need to learn how to get these answers, just a good board to think it out!
Cheers
Oh, I got the y equation from the y=f(x) as I transposed the y value across which the gave me y! Basically I'm integrating from a second derivative to find the function f(x) given y=f(x) passes through the co ordinates.

[kenny629]

Damn, I think I just do as you said (and as I thought earlier) make 2 equations with the co ordinates then solve for c and n giving me f(x)?

[notnek]

(Original post by kenny629)
Damn, I think I just do as you said (and as I thought earlier) make 2 equations with the co ordinates then solve for c and n giving me f(x)?

Is that a question? I'm not sure what you're asking.

[kenny629]

ok, ill sum up. I was given f''(x) and asked to find a genereic f(x) which well say is x^6+c(x)+n. Now i have been told that y=f(x) passes through th points (co-ordinates) mentioned above. It requires me to find f(x). Im asking now i have the genereic f(x) i just plug in these corordinates making two equatons and solve f(x) using the method of simultaneous equations?

[notnek]

(Original post by kenny629)
ok, ill sum up. I was given f''(x) and asked to find a genereic f(x) which well say is x^6+c(x)+n. Now i have been told that y=f(x) passes through th points (co-ordinates) mentioned above. It requires me to find f(x). Im asking now i have the genereic f(x) i just plug in these corordinates making two equatons and solve f(x) using the method of simultaneous equations?

Correct.

[kenny629]

Ok cool, I think I was getting too involved with the y variable! Thank you kindly!
Kenny

[kenny629]

Just to clarify to solve ill have 2^6+2c+n-8=5^6+5c+n-28.
And solve from there