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# integral

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1. integral
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!
2. Re: integral
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.
3. Re: integral
Of course! Didn't think of that, thanks!
4. Re: integral
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??
5. Re: integral
(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?
6. Re: integral
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)
7. Re: integral
Y=f(x) sorry!!!
8. Re: integral
(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.
9. Re: integral
Differentiation s the reverse of chain rule and vice versa!
10. Re: integral
(Original post by ECONMATHSMATHSMATH)
Differentiation s the reverse of chain rule and vice versa!
Huh?

The chain rule is a method of differentiation...
11. Re: integral
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!
12. Re: integral
(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?
13. Re: integral
(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
14. Re: integral
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.
Last edited by kenny629; 08-08-2012 at 19:55.
15. Re: integral
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)?
16. Re: integral
(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.
17. Re: integral
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?
18. Re: integral
(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.
19. Re: integral
Ok cool, I think I was getting too involved with the y variable! Thank you kindly!
Kenny
20. Re: integral
Just to clarify to solve ill have 2^6+2c+n-8=5^6+5c+n-28.
And solve from there

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Last updated: August 9, 2012
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