Algebra

Compute    

(2 + 3i) + (2 - 3i) + (-2 + 3i) + (-2 - 3i).     

given                                                           (2 + 3i) + (2 – 3i) + (–2 + 3i) + (–2 – 3i)    

without the parentheses                               2 + 3i + 2 – 3i – 2 + 3i – 2 – 3i    

rearranged for ease of recognition             +2 +2 –2 –2   +3i +3i –3i –3i    

looks like everything cancels out                 zero    

_.