(-2a-5)(3a+5)=0

Solution for (-2a-5)(3a+5)=0 equation:

(-2a-5)(3a+5)=0

We multiply parentheses ..

(-6a^2-10a-15a-25)=0

We get rid of parentheses

-6a^2-10a-15a-25=0

We add all the numbers together, and all the variables

-6a^2-25a-25=0

a = -6; b = -25; c = -25;
Δ = b2-4ac
Δ = -252-4·(-6)·(-25)
Δ = 25
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$a_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$a_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{25}=5$
$a_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-25)-5}{2*-6}=\frac{20}{-12}
=-1+2/3
$
$a_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-25)+5}{2*-6}=\frac{30}{-12}
=-2+1/2
$