3z(3z+20-21)=0

Solution for 3z(3z+20-21)=0 equation:

3z(3z+20-21)=0

We add all the numbers together, and all the variables

3z(3z-1)=0

We multiply parentheses

9z^2-3z=0

a = 9; b = -3; c = 0;
Δ = b2-4ac
Δ = -32-4·9·0
Δ = 9
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$z_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$z_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{9}=3$
$z_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-3)-3}{2*9}=\frac{0}{18}
=0
$
$z_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-3)+3}{2*9}=\frac{6}{18}
=1/3
$