Question

Please complete z2+9z-90=(z-6)(z+?) ...?

Answer 1

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.

Answer 2

The answer is:  (z - 6)(z + 15)

z² + 9z - 90 = z*z + 15z - 6z - 6*15 =
                    = (z*z + 15z) - (6z + 6*15) = 
                    = z(z + 15) - 6(z + 15) =
                    = (z - 6)(z + 15)