Error

Derivation

1. Initial program 0.2

   \[\left(\frac{m \cdot \left(1 - m\right)}{v} - 1\right) \cdot m\]

2. Simplified0.2

   \[\leadsto \color{blue}{\frac{m}{v} \cdot \left(m - m \cdot m\right) - m}\]

3. Taylor expanded around 0 6.7

   \[\leadsto \color{blue}{\left(\frac{{m}^{2}}{v} - \frac{{m}^{3}}{v}\right)} - m\]

4. Simplified0.2

   \[\leadsto \color{blue}{\left(\frac{m}{v} - m \cdot \frac{m}{v}\right) \cdot m} - m\]

5. Final simplification0.2

   \[\leadsto \left(\frac{m}{v} - m \cdot \frac{m}{v}\right) \cdot m - m\]

Reproduce

herbie shell --seed 2019093 
(FPCore (m v)
  :name "a parameter of renormalized beta distribution"
  :pre (and (< 0 m) (< 0 v) (< v 0.25))
  (* (- (/ (* m (- 1 m)) v) 1) m))