- $f'(x) = {2019^{{x^2} - x}}\ln 2019$.
- $f'(x) = \dfrac{{{{2019}^{{x^2} - x}}}}{{\ln 2019}}$.
- $f'(x) = (2x + 1){2019^{{x^2} - x}}\ln 2019.$
- $f'(x) = (2x - 1){2019^{{x^2} - x}}\ln 2019$.