for any non - zero a and b that satisfy | ab | = ab and | a | = a | b - 4 | + | ab - b | = ?
| ab | = ab and | a | = - a = > b is also negative . so | b - 4 | + | ab - b | = ( b - 4 ) + ab - b ( as ab is positive and - b is positive , so expression is totally positive ) = b - 4 + ab - b = ab - 4 answer - a
subtract(subtract(const_1, const_1), 4)