Initial program 0.5
\[x1 + \left(\left(\left(\left(\left(\left(\left(2 \cdot x1\right) \cdot \frac{\left(\left(3 \cdot x1\right) \cdot x1 + 2 \cdot x2\right) - x1}{x1 \cdot x1 + 1}\right) \cdot \left(\frac{\left(\left(3 \cdot x1\right) \cdot x1 + 2 \cdot x2\right) - x1}{x1 \cdot x1 + 1} - 3\right) + \left(x1 \cdot x1\right) \cdot \left(4 \cdot \frac{\left(\left(3 \cdot x1\right) \cdot x1 + 2 \cdot x2\right) - x1}{x1 \cdot x1 + 1} - 6\right)\right) \cdot \left(x1 \cdot x1 + 1\right) + \left(\left(3 \cdot x1\right) \cdot x1\right) \cdot \frac{\left(\left(3 \cdot x1\right) \cdot x1 + 2 \cdot x2\right) - x1}{x1 \cdot x1 + 1}\right) + \left(x1 \cdot x1\right) \cdot x1\right) + x1\right) + 3 \cdot \frac{\left(\left(3 \cdot x1\right) \cdot x1 - 2 \cdot x2\right) - x1}{x1 \cdot x1 + 1}\right)\]
Applied simplify0.6
\[\leadsto \color{blue}{\left(x1 + {x1}^{3}\right) + \left(\left(x1 + \left(\frac{\left(x2 - \left(x1 - x2\right)\right) + \left(x1 \cdot x1\right) \cdot 3}{1 + x1 \cdot x1} \cdot \left(\left(x1 \cdot x1\right) \cdot 3\right) + \frac{\left(x1 \cdot x1\right) \cdot 3 - \left(x1 + \left(x2 + x2\right)\right)}{\frac{1 + x1 \cdot x1}{3}}\right)\right) + \left(1 + x1 \cdot x1\right) \cdot \left(\left(\frac{4}{1 + x1 \cdot x1} \cdot \left(\left(x2 - \left(x1 - x2\right)\right) + \left(x1 \cdot x1\right) \cdot 3\right) - 6\right) \cdot \left(x1 \cdot x1\right) + \frac{\left(\left(x2 - \left(x1 - x2\right)\right) + \left(x1 \cdot x1\right) \cdot 3\right) \cdot \left(x1 + x1\right)}{1 + x1 \cdot x1} \cdot \left(\frac{\left(x2 - \left(x1 - x2\right)\right) + \left(x1 \cdot x1\right) \cdot 3}{1 + x1 \cdot x1} - 3\right)\right)\right)}\]