\(2a(a + b - c) - 2b(a - b - c) + 2c\ \cdot\)
\[\cdot (a - b + c) = 2a^{2} + 2ab - 2ac - 2ab +\]
\[+ \ 2b^{2} + 2bc + 2ac - 2bc + 2c^{2} = 2a^{2} +\]
\[+ \ 2b² + 2c²\]