There are 1 questions in this calculation: for each question, the 1 derivative of t is calculated.
    Note that variables are case sensitive.
\[ \begin{equation}\begin{split}[1/1]Find\ the\ first\ derivative\ of\ function\ \frac{6.391r}{(r + t)} - \frac{0.722}{10000}\ with\ respect\ to\ t：\\\end{split}\end{equation} \]\[ \begin{equation}\begin{split}\\Solution:&\\ &Primitive\ function\ = \frac{6.391r}{(r + t)} - 0.0000722\\&\color{blue}{The\ first\ derivative\ function：}\\&\frac{d\left( \frac{6.391r}{(r + t)} - 0.0000722\right)}{dt}\\=&6.391(\frac{-(0 + 1)}{(r + t)^{2}})r + 0 + 0\\=&\frac{-6.391r}{(r + t)(r + t)}\\ \end{split}\end{equation} \]

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