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

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

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

We multiply parentheses ..

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

We get rid of parentheses

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

We add all the numbers together, and all the variables

25b^2+15b-18=0

a = 25; b = 15; c = -18;
Δ = b2-4ac
Δ = 152-4·25·(-18)
Δ = 2025
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$b_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$b_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{2025}=45$
$b_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(15)-45}{2*25}=\frac{-60}{50}
=-1+1/5
$
$b_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(15)+45}{2*25}=\frac{30}{50}
=3/5
$