(5b+6)(3b-5)=0

Solution for (5b+6)(3b-5)=0 equation:

(5b+6)(3b-5)=0

We multiply parentheses ..

(+15b^2-25b+18b-30)=0

We get rid of parentheses

15b^2-25b+18b-30=0

We add all the numbers together, and all the variables

15b^2-7b-30=0

a = 15; b = -7; c = -30;
Δ = b2-4ac
Δ = -72-4·15·(-30)
Δ = 1849
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$b_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$b_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{1849}=43$
$b_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-7)-43}{2*15}=\frac{-36}{30}
=-1+1/5
$
$b_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-7)+43}{2*15}=\frac{50}{30}
=1+2/3
$