Factor k^2+k-72 ...

(k + 9) (k - 8)

Step-by-step explanation:

Given

k² + k - 72

Consider the factors of the constant term ( - 72) which sum to give the coefficient of the k - term ( + 1)

The factors are + 9 and - 8, since

9 * - 8 = - 72 and 9 + 8 = + 1, hence

k² + k - 72 = (k + 9) (k - 8)