There are 1 questions in this calculation: for each question, the 1 derivative of t is calculated.
    Note that variables are case sensitive.
\[ \begin{equation}\begin{split}[1/1]Find\ the\ first\ derivative\ of\ function\ p - c - \frac{D(t)(p + c + f)(t)(b - (p + c + f))}{D}\ with\ respect\ to\ t：\\\end{split}\end{equation} \]\[ \begin{equation}\begin{split}\\Solution:&\\ &Primitive\ function\ = - pbt^{2} - cbt^{2} + p^{2}t^{2} + 2pct^{2} + 2pft^{2} + c^{2}t^{2} + 2cft^{2} - fbt^{2} + p - c + f^{2}t^{2}\\&\color{blue}{The\ first\ derivative\ function：}\\&\frac{d\left( - pbt^{2} - cbt^{2} + p^{2}t^{2} + 2pct^{2} + 2pft^{2} + c^{2}t^{2} + 2cft^{2} - fbt^{2} + p - c + f^{2}t^{2}\right)}{dt}\\=& - pb*2t - cb*2t + p^{2}*2t + 2pc*2t + 2pf*2t + c^{2}*2t + 2cf*2t - fb*2t + 0 + 0 + f^{2}*2t\\=& - 2pbt - 2cbt + 2p^{2}t + 4pct + 4pft + 2c^{2}t + 4cft - 2fbt + 2f^{2}t\\ \end{split}\end{equation} \]

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