Find the derivative of 101-x2. 1.) So, I used power rule to get: (1-x2)(10-x2). 2.) Then I did chain rule and multiplied my previous answer with (d/dx)(-x2). 3.) The answer I get is: (-2x)(1-x2)(10-x2). When I use my calculator, the answer I get is: -20*ln(10)*10-x2. So, where does -20*ln(10) come from?