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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 $2x$.

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 $2x$.