Suppose we have a function $\displaystyle f(x)$ defined on the interval $\displaystyle [x_1,x_2]$ whose antiderivative is $\displaystyle F(x) + C$.

If $\displaystyle F(x_1) = K_1$ and $\displaystyle F(x_2) = K_2$ then how does one determine the value of $\displaystyle C$?

Thanks!