0=25z^2-4

Solution for 0=25z^2-4 equation:

0=25z^2-4

We move all terms to the left:

0-(25z^2-4)=0

We add all the numbers together, and all the variables

-(25z^2-4)=0

We get rid of parentheses

-25z^2+4=0

a = -25; b = 0; c = +4;
Δ = b2-4ac
Δ = 02-4·(-25)·4
Δ = 400
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$z_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$z_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{400}=20$
$z_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(0)-20}{2*-25}=\frac{-20}{-50}
=2/5
$
$z_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(0)+20}{2*-25}=\frac{20}{-50}
=-2/5
$