The difference quotient is an expression used in single-variable calculus to find the derivative of a function. It is usually represented by the expression (f-f(x))/h, where h approaches 0. The difference quotient formula is a part of the definition of the derivative of a function, and it gives the slope of a secant line that is drawn to a curve. The difference quotient is used to calculate the slope of the secant line between two points on the graph of a function, f. The difference quotient is also known as the Newton quotient or Fermats difference quotient.