I introduced these first two in my calculus class as examples of other methods, but since we had already covered differentiation and the students who were continuing on to second semester calculus would deal with Taylor series, I used the following method. Suppose we differentiate both sides of Equation 3. Note that c((x + 1) − x) = c, so upon differentiation, the c term will vanish. Differentiating Equation 3 once: