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

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