Y square - y - 20 (factorisation)

(y - 5) (y + 4)

Step-by-step explanation:

Given

y² - y - 20

Consider the factors of the constant term ( - 20) which sum to give the coefficient of the y - term ( - 1)

The factors are - 5 and + 4, since

- 5 * 4 = - 20 and - 5 + 4 = - 1, thus

y² - y - 20 = (y - 5) (y + 4) ← in factored form