Why do different functions like $x^2$ and $x^2 + C$ share the same derivative 2x?

The '$+C$' term represents the arbitrary constant of integration. It signifies that on a connected interval, all antiderivatives of a given function differ from one another by a constant.

Conditions: The domain is a connected interval.; The function being integrated has at least one antiderivative.

The indefinite integral of $2x$ is $x^2+C$. In this context, the term 'indefinite integral' is simply another name for the antiderivative, representing the family of all functions whose derivative is $2x$.

Conditions: The expression being integrated is $2x$.; The result includes an arbitrary constant $C$.

The indefinite integral is simply another name for the antiderivative. Both terms refer to the family of functions whose derivative is the given function, typically expressed with an arbitrary constant $C$.

Conditions: The context is introductory calculus focusing on reverse differentiation.; The function is continuous or differentiable on the interval of interest.

Integral notation is introduced early as a shorthand for antiderivatives to avoid writing cumbersome sentences. Its deeper geometric meaning, relating to areas under curves and sums of rectangles, will be motivated later when the course covers definite integrals.

Conditions: The current focus is on understanding antiderivatives.; The course will later cover definite integrals and areas under curves.

The notation $\int 2x \, dx$ is a compact way to ask for the antiderivative of $2x$ with respect to $x$. It represents the entire family of functions whose derivative is $2x$, which is written as $x^2+C$.

Conditions: The variable of integration is $x$.; The integrand is $2x$.