TeX source:

\mathbf{D}\left(\mathrm{f}^{\mathrm{n}}(\mathrm{x})\right)=\mathrm{n} \mathrm{f}^{\mathrm{n}-1}(\mathrm{x}) \cdot \mathbf{D}(\mathbf{f}(\mathbf{x})) . \mathbf{D}\left(\mathrm{f}^{5}\right)=5 \mathrm{f}^{4} \mathbf{D}(\mathbf{f})