Given,

y² + y – 72

Now, first we have to find out the numbers whose-

Sum = 1 and

Product = - 72

The numbers are 9 and 8,

So,

y² + y – 72

= y² + 9y – 9y – 72

= y(y + 9) – 9(y + 9)

= (y + 9)(y – 9)