Question 461672


{{{a - 2b + 3c -(a - 2b - 3c + d)}}}

={{{a - 2b + 3c -a + 2b + 3c - d}}}

={{{cross(a) - cross(2b) + 3c -cross(a) + cross(2b) + 3c - d}}}

={{{6c - d}}}