There are 1 questions in this calculation: for each question, the 1 derivative of x is calculated.
    Note that variables are case sensitive.
\[ \begin{equation}\begin{split}[1/1]Find\ the\ first\ derivative\ of\ function\ cos(3x + 2y) + cos(2x + 4y) - 2sin(x + y)\ with\ respect\ to\ x：\\\end{split}\end{equation} \]\[ \begin{equation}\begin{split}\\Solution:&\\ &\color{blue}{The\ first\ derivative\ function：}\\&\frac{d\left( cos(3x + 2y) + cos(2x + 4y) - 2sin(x + y)\right)}{dx}\\=&-sin(3x + 2y)(3 + 0) + -sin(2x + 4y)(2 + 0) - 2cos(x + y)(1 + 0)\\=&-3sin(3x + 2y) - 2sin(2x + 4y) - 2cos(x + y)\\ \end{split}\end{equation} \]

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