(6z+5)(z+5)=0

Solution for (6z+5)(z+5)=0 equation:

(6z+5)(z+5)=0

We multiply parentheses ..

(+6z^2+30z+5z+25)=0

We get rid of parentheses

6z^2+30z+5z+25=0

We add all the numbers together, and all the variables

6z^2+35z+25=0

a = 6; b = 35; c = +25;
Δ = b2-4ac
Δ = 352-4·6·25
Δ = 625
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$z_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$z_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{625}=25$
$z_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(35)-25}{2*6}=\frac{-60}{12}
=-5
$
$z_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(35)+25}{2*6}=\frac{-10}{12}
=-5/6
$