(b+4)(2b+1)=0

Solution for (b+4)(2b+1)=0 equation:

(b+4)(2b+1)=0

We multiply parentheses ..

(+2b^2+b+8b+4)=0

We get rid of parentheses

2b^2+b+8b+4=0

We add all the numbers together, and all the variables

2b^2+9b+4=0

a = 2; b = 9; c = +4;
Δ = b2-4ac
Δ = 92-4·2·4
Δ = 49
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$b_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$b_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{49}=7$
$b_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(9)-7}{2*2}=\frac{-16}{4}
=-4
$
$b_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(9)+7}{2*2}=\frac{-2}{4}
=-1/2
$