$\int f(x)\,\mathrm{d}x = \left(\int_0^x f(t) \, \mathrm{d}t\right) + C$ If $f(x)$ is a continuous function on $\mathbb{R}$ and I am asked to find 
$\int f(x) \, dx$, what is the problem with the following answer:
$$\int f(x)\,\mathrm{d}x = \left(\int_0^x f(t) \, \mathrm{d}t\right) + C$$


The problem with your answer is the problem with your answer.

And I hope the problem with my answer will tell you something about the problem with your answer.
