Factorize

y³ + y² – y – 1

Let p(y) = y³ + y² – y – 1

On taking y² common from first two terms in p(y), we get,

p (y) = y²(y + 1) –1(y + 1)

Now, taking (y + 1) common, we get,

⇒ p(y) = (y² – 1)(y + 1)

As we know the identity, (y² – 1) = (y + 1)(y – 1)

⇒ p(y) = (y – 1)(y + 1)(y + 1)