a^2b - [ 2(a^2 - 2a^2c) - ( 2b^2c - a^2c)]= a^2b - [ 2a^2 - 4a^2c - 2b^2c + a^2c ]= a^2b - 2a^2 + 4a^2c - 2b^2c +a^2c= a^2b - 2a^2 +5a^2c - 2b^2c
