Derivative of 6x-x^3

1. Differentiate $- x^{3} + 6 x$ term by term:

   1. The derivative of a constant times a function is the constant times the derivative of the function.

      1. Apply the power rule: $x$ goes to $1$

      So, the result is: $6$

   2. The derivative of a constant times a function is the constant times the derivative of the function.

      1. Apply the power rule: $x^{3}$ goes to $3 x^{2}$

      So, the result is: $- 3 x^{2}$

   The result is: $6 - 3 x^{2}$

The answer is:

$$6 - 3 x^{2}$$