1)

[tex]f(x) = {x}^{3} \cos(x) \\ f'(x) = ( {x}^{3} )' \cos(x) + {x}^{3} ( \cos(x) )' = \\ 3 {x}^{3 - 1} \cos(x) + {x}^{3} \times ( - \sin(x) ) = \\ 3 {x}^{2} \cos(x) - {x}^{3} \sin(x) [/tex]

2)

[tex]f(x) = (2x - 1) \sin(x) \\ f'(x) = (2x - 1)' \sin(x) + (2x - 1)( \sin(x) )' = \\ 2 \sin(x) + (2x - 1) \cos(x) [/tex]