Which of the following is true regarding the definite integral ∫13f(x)dx\int_{1}^{3} f(x) dx∫13f(x)dx?
It is always a function of xxx.
It represents the net signed area between the curve and the x-axis.
It is always positive.
It is equal to f(3)−f(1)f(3) - f(1)f(3)−f(1).