He was asking you if you worked toward obtaining a raise in your current job… Your answer is needlessly agressive, and irrelevent to what is actually written.

I’m just being a pendant here, but the derivative of x²+C is 2x. You put the constant at the wrong place.

Also, i’m glad you found a textbook well suited for you. I have to wonder what you mean by ‘why’, do you mean a proof?