Use long division.
y - 1
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y³+1 | y⁴ - y³ + 2y² + y - 1
y⁴ + y
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- y³ + 2y² - 1
- y³ - 1
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2y²
Answer: y - 1 + 2y2 ÷ y³+1
Note:
The correct answer should be written with parenthesis, as y - 1 + y²/(y³+1) in order to avoid ambiguity.