Evaluate the variable expression when a = 5, b = 5, and c = -2. bc : (2a) Evaluate the variable expression when a = 4, b = 7, and c = -4. (b - 2a)2 + bc Evaluate the variable expression when a = 2, b = 3, and c = -1. b2 - 4ac Evaluate the variable expression when a = -2, b = 5, c = -2, and d = 3. b - 6a bc2 - d Evaluate the variable expression when a = 4 and c = -6. a - 2c