There are 1 questions in this calculation: for each question, the 1 derivative of x is calculated.
    Note that variables are case sensitive.
\[ \begin{equation}\begin{split}[1/1]Find\ the\ first\ derivative\ of\ function\ (4 + \frac{2}{5}n)(20 - n)\ with\ respect\ to\ x：\\\end{split}\end{equation} \]\[ \begin{equation}\begin{split}\\Solution:&\\ &Primitive\ function\ = 4n - \frac{2}{5}n^{2} + 80\\&\color{blue}{The\ first\ derivative\ function：}\\&\frac{d\left( 4n - \frac{2}{5}n^{2} + 80\right)}{dx}\\=&0 + 0 + 0\\=&0\\ \end{split}\end{equation} \]

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