Answer: a
Step-by-step explanation:
(6z³+3z²-4z+8) - (4z²-3z+2)
all of the numbers in the second set of parenthesis are going to have their signs switched so...
(6z³+3z²-4z+8) + (-4z²+3z-2)
now you add the two sets of parenthesis
6z³ - z² - z + 6
