Complete z^2+9z-90=(z-6)(z+?)

To complete the equation z^2+9z-90=(z-6)(z+?), we need to find the missing value that, when distributed with z-6, will result in z^2+9z-90.

To solve for this, let's expand the right side of the equation:

(z-6)(z+?) = z^2+z(-6)+?(z)+?(6)

Expanding further:

z^2+z(-6)+?(z)+?(6) = z^2-6z+?z+?(6)

Comparing this equation to the original equation z^2+9z-90, we can see that the constant term in both equations is -90, and the coefficient of z in the original equation is 9.

To find the missing value, we need to find the value that, when multiplied with (z-6), will result in a constant term of -90. In other words, we need to find a value that, when multiplied by 6, will give us 90 (since the negative sign is already present in the equation).

The value that satisfies this is -15, as -15 * 6 = -90. Therefore, the missing value is -15.

So the complete equation is z^2+9z-90=(z-6)(z-15).