The derivative of a constant is always zero because a constant's value does not change.

When differentiating a sum of functions, you can differentiate each function separately and then add the results.

When differentiating a difference of functions, you can differentiate each function separately and then subtract the results.

A constant multiplying a function remains as a multiplier when you take the derivative of the function.

If $f(x) = c$, then $f'(x) = 0$.

If $f(x) = g(x) + h(x)$, then $f'(x) = g'(x) + h'(x)$.

If $f(x) = g(x) - h(x)$, then $f'(x) = g'(x) - h'(x)$.

If $f(x) = c cdot g(x)$, then $f'(x) = c cdot g'(x)$.

Apply the sum/difference rule and constant multiple rule: $f'(x) = 6x + 5$.

Apply the constant rule: $f'(x) = 0$.

Apply the sum/difference rule and constant multiple rule: $f'(x) = 12x^2 - 2$.

Apply the sum rule, constant rule, and constant multiple rule: $f'(x) = 20x^3$.

Apply the difference rule and constant multiple rule: $f'(x) = 4x - 6$.