4 3 / 2 5\ 7*a *(a + 3) - a *\21*a + 7*a - 3*a /
3 / 2 5\ 4 a *\-21*a - 7*a + 3*a / + a *(21 + 7*a)
3 / 5 2 \ 4 - a *\- 3*a + 7*a + 21*a/ + 7*a *(3 + a)
-a^3*(7.0*a^2 + 21.0*a - 3.0*a^5) + 7.0*a^4*(3.0 + a)
3 / 5 2 \ 4 - a *\- 3*a + 7*a + 21*a/ + 7*a *(3 + a)
3 / 5 2 \ 4 - a *\- 3*a + 7*a + 21*a/ + 7*a *(3 + a)