There are 1 questions in this calculation: for each question, the 1 derivative of x is calculated.
    Note that variables are case sensitive.
\[ \begin{equation}\begin{split}[1/1]Find\ the\ first\ derivative\ of\ function\ xr + xs + xt + xm\ with\ respect\ to\ x：\\\end{split}\end{equation} \]\[ \begin{equation}\begin{split}\\Solution:&\\ &Primitive\ function\ = rx + sx + tx + mx\\&\color{blue}{The\ first\ derivative\ function：}\\&\frac{d\left( rx + sx + tx + mx\right)}{dx}\\=&r + s + t + m\\ \end{split}\end{equation} \]

Your problem has not been solved here? Please take a look at the  hot problems ！