Z^2 + 9z - 90 = (z - 6) (z + )

Complete.

(z - 6) (z + 15)

Step-by-step explanation:

Given

z² + 9z - 90

Consider the factors of the constant term ( - 90) which sum to give the coefficient of the z - term ( + 9)

The factors are - 6 and + 15, since

- 6 * 15 = - 90 and - 6 + 15 = + 9, hence

z² + 9z - 90 = (z - 6) (z + 15)