## onegirl 2 years ago Find the function f(x) satisfying the given conditions. (HINT: You are finding the value of C)

1. onegirl

2. myininaya

Find $\int\limits_{}^{}f'(x) dx=f(x)+C, \text{ where } (f)'=f'$

3. myininaya

Or evaluate

4. myininaya

Integrate the function given to get from f' to f.

5. myininaya

Don't forget when you integrate, put +C.

6. onegirl

can u explain? :/

7. myininaya

$\int\limits_{}^{}f'(x) dx=\int\limits_{}^{}(4x^2-1) dx$ You may find it easy to use the following: $\int\limits_{}^{}x^n dx =\frac{x^{n+1}}{n+1}+C, n \neq -1$ This is because $(\frac{x^{n+1}}{n+1})'=(n+1) \cdot \frac{x^{n+1-1}}{n+1}=x^{n+1-1}=x^n$ And you may also want to use $\int\limits_{}^{}k dx=kx+C \text{ where} K, C \text{ are a constant}$

8. myininaya

This is because (kx+C)'=(kx)'+(C)'=k(x)'+0+k(x)'=k(1)=k

9. onegirl

okay thanks

10. zepdrix

Are you familiar with the idea of Integration yet? Or has it only been introduced to you as the process of finding the anti-derivative so far?

11. onegirl

no i'm not familiar

12. onegirl

@Best_Mathematician can u help?

13. Loser66

|dw:1367625325100:dw|

14. Loser66

so, when you have f' (4x^2 +1) take integral to get back the original function. . when take integral, the solution for that method always a family solution. in case they give you the special solution, that means they want you to pick out just special C in set of family solution . take integral of f' you have f(x) = 4x^3/3 -x +C and when they give you f(0) =2 just plug 0 into the function you' ve just got. to find C f(0) = 4 *0^3/3 -0 +C = 2 ---> C =2 that's it

15. onegirl

ohhh okay

16. Loser66

sorry , one more step. plug C back to f(x) = 4x^3/3 - x +2

17. Loser66

I 'm supper dummy at teaching, hope you can understand what i mean

18. onegirl

so plugging 2 back into f(x) = 4x^3/3 - x + 2 right?

19. Loser66

yep

20. onegirl

okay

21. onegirl

i got 32/3 or 10.6666

22. Loser66

hey, you misunderstand the concept, they ask you to find out C, and you got C =2 that's it. just plug C =2 into the function, nothing to do more.

23. onegirl