Answer:
-y³ -6y²x +30
Explanation:
When parentheses are eliminated and the y variable placed first in each term, the expression simplifies to ...
... 15 -7y²x -y³ +y²x +15
Arranging like terms together, we have ...
... -y³ +y²x(-7 +1) +(15 +15)
... -y³ -6y²x +30
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The two different 3rd-degree terms can be expressed in either order. I have chosen to list the term with the largest exponent first. The expression could also be written with the same-degree terms in "lexicographical order", meaning the expression would be written ...
... -6xy² -y³ +30