What should be added to \[xy+yz+zx\] to get\[-xy-yz-zx\]?

1.	What should be added to \[xy+yz+zx\] to get\[-xy-yz-zx\]?
A.	\[-2xy-2yz-2zx\]
B.	\[-3xy-yz-zx\]
C.	\[-3xy-3yz-3zx\]
D.	\[-3xy-yz\]
Answer» B. \[-3xy-yz-zx\]

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