Answer:
Answer would be 15.
Step-by-step explanation:
We have to complete the expression given as
\(z^{2}+9z-90=(z-6)(z+?))\)
We will try to factorize the expression given in the left side.
\(z^{2}+9z-90=z^{2}+15z-6z-90\)
= z(z+15)-6(z-15)
=\((z-6)(z-15)\)
Now we will compare this factorized form with the right side of the expression.
(z-6) (z-15) (= (z-6) (z+?)
We find question mark is 15.
Therefore, the answer is 15.
