2d. 0. −18g. a2. −21x3. 0. 3mn. 0. −3a3b3c3. −9abcd. 1. 12. 4. −18. 10. Exercise16. 30a5. 40a4b3. 63x2y2. 2a5b5c2. 9a7b9c9. −10a2. 12ab. −a4b3. 10a5b5c. 12x7y5z2.