Найдите промежутки возрастания и убывания функции : f(x)=2x^3-9x^2-24

[latex]f(x)=2x^3-9x^2-24, \\ f'(x)=6x^2-18x, \\ f'(x)=0, \ 6x^2-18x=0, \\ 6x(x-3)=0, \\ x_1=0, x_2=3; \\ x\ \textless \ 0, \ f'(x)\ \textgreater \ 0, \ f(x)\nearrow, \\ 0\ \textless \ x\ \textless \ 3, \ f'(x)\ \textless \ 0, \ f(x)\searrow, \\ x\ \textgreater \ 3, \ f'(x)\ \textgreater \ 0, \ f(x)\nearrow.[/latex]