(2x+5)(2x+4)=0

Solution for (2x+5)(2x+4)=0 equation:

(2x+5)(2x+4)=0

We multiply parentheses ..

(+4x^2+8x+10x+20)=0

We get rid of parentheses

4x^2+8x+10x+20=0

We add all the numbers together, and all the variables

4x^2+18x+20=0

a = 4; b = 18; c = +20;
Δ = b2-4ac
Δ = 182-4·4·20
Δ = 4
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{4}=2$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(18)-2}{2*4}=\frac{-20}{8}
=-2+1/2
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(18)+2}{2*4}=\frac{-16}{8}
=-2
$