-4(z-1)(-z-2)=0

Solution for -4(z-1)(-z-2)=0 equation:

-4(z-1)(-z-2)=0

We add all the numbers together, and all the variables

-4(z-1)(-1z-2)=0

We multiply parentheses ..

-4(-1z^2-2z+z+2)=0

We multiply parentheses

4z^2+8z-4z-8=0

We add all the numbers together, and all the variables

4z^2+4z-8=0

a = 4; b = 4; c = -8;
Δ = b2-4ac
Δ = 42-4·4·(-8)
Δ = 144
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$z_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$z_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{144}=12$
$z_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(4)-12}{2*4}=\frac{-16}{8}
=-2
$
$z_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(4)+12}{2*4}=\frac{8}{8}
=1
$