Bonjour,
[tex]f(x) = \frac{1}{12} {x}^{3} + \frac{1}{4}x {}^{2} - 2x - 1[/tex]
[tex]f'(x) = \frac{1}{12} \times 3 \times {x}^{2} + \frac{1}{4} \times 2 \times x - 2[/tex]
[tex]f'(x) = \frac{3}{12} {x}^{2} + \frac{2}{4} x - 2[/tex]
[tex]f'(x) = \frac{1}{4} {x}^{2} + \frac{1}{2} x - 2[/tex]
