(5b+8)(b-8)=0

Solution for (5b+8)(b-8)=0 equation:

(5b+8)(b-8)=0

We multiply parentheses ..

(+5b^2-40b+8b-64)=0

We get rid of parentheses

5b^2-40b+8b-64=0

We add all the numbers together, and all the variables

5b^2-32b-64=0

a = 5; b = -32; c = -64;
Δ = b2-4ac
Δ = -322-4·5·(-64)
Δ = 2304
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$b_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$b_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{2304}=48$
$b_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-32)-48}{2*5}=\frac{-16}{10}
=-1+3/5
$
$b_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-32)+48}{2*5}=\frac{80}{10}
=8
$