Determine the sum: (2abc − 9abc2 − 14ab2c) + (−5abc + 4ab2c). −12a5b7c6 −21a3b4c4 − a2b3c2 −3abc − 9abc2 − 10ab2c −3a2b2c2 − 9a2b2c4 − 10a2b4c2

Step-by-step explanation:

Remove the parentheses, to make it easier to spot and add up "like terms."

(2abc − 9abc2 − 14ab2c) + (−5abc + 4ab2c). becomes

2abc − 9abc2 − 14ab2c − 5abc + 4ab2c

Now group "abc" terms together and combine them:

2abc

-5abc

-3abc

And so we now have -3abc - 9abc² − 14ab2c  + 4ab2c

Combining the ab²c terms results in  the final

-3abc - 9abc² − 10ab²c      This matches the 3rd answer choice.

Note:  To indicate "the sqare of c," write " c² " or  " c^2. "

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step-by-step explanation:

391.6 is the correct answer