Simplify the following text for a Grade 3 native English-speaking person.
Original: The Fundamental Theorem of Calculus is a theorem that says , where F ( x ) is the antiderivative of f ( x ) . It states that the area under a curve , from a point where x = a to a point where x = b , is equal to the the antiderivative of the function at b , minus the antiderivative of the function at a.
Simplified: Here , and we can use as the antiderivative .