Use the definition of the derivative to prove that d dx 2x 3/7 Consider the function f(x) = x2, with x # 0. Let me rewrite it as x2 = x+ ... +x. x times If I now differentiate both sides of the equation, I get 2x = 1+...+ 1. x times But the right-hand-side is simply x, hence I get 2x = x. Since I assumed that x / 0, I can divide by x on both sides of the equation to get 2 = 1. Crazy! What's wrong