This is what you would consider the antiderivative of 2x. That's all nice, but this is kind of clumsy to have to write a sentence like this, so let's come up with some notation for the antiderivative. The convention here is to use a strange-looking notation. It's to use a big, elongated, S-looking thing like that, and a dx around the function that you're trying to take the antiderivative of. In this case, it would look something like this. This is just saying this is equal to the antiderivative of 2x, and the antiderivative of 2x, we have already seen, is x squared plus c. Now, you might be saying, why do we use this type of crazy notation? It will become more obvious when we study the definite integral and areas under curves, and taking sums of rectangles in order to approximate the area of the curve.