The past, present, and future

Algebra Level 4

Given that \[ \mathscr{E} = \dfrac{a^3 -b^3 -c^3 - 3abc}{a^2 + b^2 + c^2 + ab - bc + ac} \]

and \( a = 2015, b = 2016, c = 2017 \). Find \( \mathscr{E}\).