5b(7b+4)=0

Solution for 5b(7b+4)=0 equation:

5b(7b+4)=0

We multiply parentheses

35b^2+20b=0

a = 35; b = 20; c = 0;
Δ = b2-4ac
Δ = 202-4·35·0
Δ = 400
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$b_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$b_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{400}=20$
$b_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(20)-20}{2*35}=\frac{-40}{70}
=-4/7
$
$b_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(20)+20}{2*35}=\frac{0}{70}
=0
$