Integration (Constant Of Integration In Definite Integrals)

[Ted_Grendy]

Hello

I am trying to understand definite integrate but I was stuck due to the constant of integration (+c). I know what the +c is and why its there however, given the function:-

1. f(x) = x^2

If I differentiated it I would get:-

2. dy/dx = 2x

Now If I was told to integrate 2x between 4 and 8 (to find the area under this curve between 4 and 8) then I would do the following:-

3. Int(2x) = x^2+c

4. (8^2+c) - (4^2+c)

5. 48+2c

I cannot seem to get rid of the +C?

I was told that I don't need the +C when finding the definite integral but to me it seems important to have otherwise the area would be wrong?

Can anyone explain?

Thank you.

 

[HallsofIvy]

Where did you get the idea that c- c was equal to 2c?

 

[Ted_Grendy]

Where did you get the idea that c- c was equal to 2c?

Got it, thanks